SCHEDULE 13G

Amendment No. 2 
Nucor Corporation 
Common Stock 
Cusip #670346105 


Cusip #670346105 
Item 1:	Reporting Person - FMR Corp.
Item 4:	Delaware
Item 5:	826,249 
Item 6:	0 
Item 7:	4,037,549 
Item 8:	0 
Item 9:	4,037,549 
Item 11:	2.595% 
Item 12:	    HC


Cusip #670346105  
Item 1:	Reporting Person - Edward C. Johnson 3d 
Item 4:	United States of America
Item 5:	0 
Item 6:	0 
Item 7:	4,037,549 
Item 8:	0 
Item 9:	4,037,549 
Item 11:	2.595% 
Item 12:	IN 




	SCHEDULE 13G - TO BE INCLUDED IN 
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)




Item 1(a).	Name of Issuer:	

		Nucor Corporation 

Item 1(b).	Name of Issuer's Principal Executive Offices:

		2100 Rexford Road  
		Charlotte, NC  28211
		  

Item 2(a).	Name of Person Filing: 

		FMR Corp.

Item 2(b).	Address or Principal Business Office or, if None, 
Residence:

		82 Devonshire Street, Boston, 
Massachusetts  02109

Item 2(c).	Citizenship:

		Not applicable

Item 2(d).	Title of Class of Securities:

		Common Stock 

Item 2(e).	CUSIP Number:  

		670346105 

Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b) 
and the person filing, FMR Corp., is a parent holding company 
in accordance with Section 240.13d-1(b)(ii)(G).  (Note:  See 
Item 7).

Item 4.	Ownership

	(a)	Amount Beneficially Owned:	4,037,549 

	(b)	Percent of Class:	2.595% 

	(c)	Number of shares as to which such 
person has:  

	(i)	sole power to vote or to direct 
the vote:	826,249 

	(ii)	shared power to vote or to 
direct the vote:	0 

	(iii)	sole power to dispose or to 
direct the disposition of:	4,037,549 

	(iv)	shared power to dispose or to 
direct the disposition of:	0 



Item 5.	Ownership of Five Percent or Less of a Class.

	If this statement is being filed to report the fact that as of the 
date hereof, the reporting person has ceased to be the 
beneficial owner of more than five percent of the class of 
securities, check the following (X).

Item 6.	Ownership of More than Five Percent on Behalf of Another 
Person.

	Not applicable

Item 7.	Identification and Classification of the Subsidiary Which 
Acquired the Security Being Reported on By the Parent 
Holding Company.

	See attached Exhibit A. 

Item 8.	Identification and Classification of Members of 
the Group.

	Not applicable.  See attached Exhibit A. 

Item 9.	Notice of Dissolution of Group.

	Not applicable.

Item 10.	Certification.

	Inasmuch as the reporting persons are no longer the beneficial 
owners of more than five percent of the number of shares 
outstanding, the reporting persons have no further reporting 
obligation under Section 13(d) of the Securities and Exchange 
Commission thereunder, and the reporting persons have no 
obligation to amend this Statement if any material change 
occurs in the facts set forth herein.

Signature

	After reasonable inquiry and to the best of my knowledge and 
belief, I certify that the information set forth in this statement 
is true, complete and correct. 

February 14, 2006 			
Date

/s/Eric D. Roiter			
Signature

Eric D, Roiter			
Duly authorized under Power of Attorney
dated December 30, 1997 by and on behalf of FMR Corp. and 
its direct and indirect subsidiaries


	SCHEDULE 13G - TO BE INCLUDED IN 
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



	Pursuant to the instructions in Item 7 of Schedule 13G, 
Fidelity Management & Research Company ("Fidelity"), 82 
Devonshire Street, Boston, Massachusetts 02109, a wholly-
owned subsidiary of FMR Corp. and an investment adviser 
registered under Section 203 of the Investment Advisers Act 
of 1940, is the beneficial owner of 3,162,130 shares or 2.032% 
of the Common Stock outstanding of Nucor Corporation  ("the 
Company") as a result of acting as investment adviser to 
various investment companies registered under Section 8 of 
the Investment Company Act of 1940.

	Edward C. Johnson 3d and FMR Corp., through its 
control of Fidelity, and the funds each has sole power to 
dispose of the 3,162,130 shares owned by the Funds.

	Members of the family of Edward C. Johnson 3d, 
Chairman of FMR Corp., are the predominant owners, directly 
or through trusts, of Series B shares of common stock of FMR 
Corp., representing 49% of the voting power of FMR Corp.  
The Johnson family group and all other Series B shareholders 
have entered into a shareholders' voting agreement under 
which all Series B shares will be voted in accordance with the 
majority vote of Series B shares.  Accordingly, through their 
ownership of voting common stock and the execution of the 
shareholders' voting agreement, members of the Johnson 
family may be deemed, under the Investment Company Act of 
1940, to form a controlling group with respect to FMR Corp.

	Neither FMR Corp. nor Edward C. Johnson 3d, 
Chairman of FMR Corp., has the sole power to vote or direct 
the voting of the shares owned directly by the Fidelity Funds, 
which power resides with the Funds' Boards of Trustees.  
Fidelity carries out the voting of the shares under written 
guidelines established by the Funds' Boards of Trustees.

	Fidelity Management Trust Company, 82 Devonshire 
Street, Boston, Massachusetts 02109, a wholly-owned 
subsidiary of FMR Corp. and a bank as defined in Section 
3(a)(6) of the Securities Exchange Act of 1934, is the 
beneficial owner of  468,621 shares or 0.301% of the 
Common Stock outstanding of the Company as a result of its 
serving as investment manager of the institutional account(s).

	Edward C. Johnson 3d and FMR Corp., through its 
control of Fidelity Management Trust Company, each has sole 
dispositive power over 468,621 shares and sole power to vote 
or to direct the voting of 335,321 shares, and no power to vote 
or to direct the voting of 133,300 shares of Common Stock 
owned by the institutional account(s) as reported above.

	Strategic Advisers, Inc., 82 Devonshire Street, Boston, 
MA 02109, a wholly-owned subsidiary of FMR Corp. and an 
investment adviser registered under Section 203 of the 
Investment Advisers Act of 1940, provides investment 
advisory services to individuals.  As such, FMR Corp.'s 
beneficial ownership includes 598 shares, or 0.000%, of the 
Common Stock stock outstanding of Nucor Corporation, 
beneficially owned through Strategic Advisers, Inc.

	Fidelity International Limited ("FIL"), Pembroke Hall, 
42 Crow Lane, Hamilton, Bermuda, and various foreign-based 
subsidiaries provide investment advisory and management 
services to a number of non-U.S. investment companies and 
certain institutional investors.  FIL, which is a qualified 
institution under section 240.13d-1(b)(1) pursuant to an SEC 
No-Action letter dated October 5, 2000, is the beneficial 
owner of 406,200 shares or 0.261% of the Common Stock 
outstanding of the Company.

	A partnership controlled predominantly by members of 
the family of Edward C. Johnson 3d, Chairman of FMR Corp. 
and FIL, or trusts for their benefit, owns shares of FIL voting 
stock with the right to cast approximately 38% of the total 
votes which may be cast by all holders of FIL voting stock.  
FMR Corp. and FIL are separate and independent corporate 
entities, and their Boards of Directors are generally composed 
of different individuals.

	FMR Corp. and FIL are of the view that they are not 
acting as a "group" for purposes of Section 13(d) under the 
Securities Exchange Act of 1934 (the "1934" Act) and that 
they are not otherwise required to attribute to each other the 
"beneficial ownership" of securities "beneficially owned" by 
the other corporation within the meaning of Rule 13d-3 
promulgated under the 1934 Act.  Therefore, they are of the 
view that the shares held by the other corporation need not be 
aggregated for purposes of Section 13(d). However, FMR 
Corp. is making this filing on a voluntary basis as if all of the 
shares are beneficially owned by FMR Corp. and FIL on a 
joint basis.



	SCHEDULE 13G - TO BE INCLUDED IN 
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)
	RULE 13d-1(f)(1)  AGREEMENT

	The undersigned persons, on February 14, 2006, agree 
and consent to the joint filing on their behalf of this Schedule 
13G in connection with their beneficial ownership of the 
Common Stock of Nucor Corporation at December 31, 2005.

	FMR Corp.

	By /s/ Eric D. Roiter			
	Eric D. Roiter
	Duly authorized under Power of Attorney dated 
December 30, 1997, by and on behalf of FMR Corp. and its 
direct and indirect subsidiaries

	Edward C. Johnson 3d

	By /s/ Eric D. Roiter			
	Eric D. Roiter
	Duly authorized under Power of Attorney dated 
December 30, 1997, by and on behalf of Edward C. Johnson 
3d

	Fidelity Management & Research Company

	By /s/ Eric D. Roiter			
	Eric D. Roiter
	Senior V.P. and General Counsel