Stock-Based Compensation (Summary Of Nucor's Restricted Stock Unit Activity Under AIP And LTIP) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested at beginning of year, Shares	962
Granted, Shares	1,101
Vested, Shares	(884)
Canceled, Shares	(20)
Unvested at June 30, 2012, Shares	1,159
Shares reserved for future grants (stock options and RSUs)	11,834
Unvested at beginning of year, Grant Date Fair Value	$ 46.09
Granted, Grant Date Fair Value	$ 35.76
Vested, Grant Date Fair Value	$ 40.26
Canceled, Grant Date Fair Value	$ 40.73
Unvested at June 30, 2012, Grant Date Fair Value	$ 40.81
AIP And LTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested at beginning of year, Shares	94
Granted, Shares	122
Vested, Shares	(144)
Unvested at June 30, 2012, Shares	72
Shares reserved for future grants (stock options and RSUs)	1,360
Unvested at beginning of year, Grant Date Fair Value	$ 42.46
Granted, Grant Date Fair Value	$ 42.20
Vested, Grant Date Fair Value	$ 41.62
Unvested at June 30, 2012, Grant Date Fair Value	$ 43.72