Stock-Based Compensation (Summary Of Nucor's Restricted Stock Unit Activity Under Annual Incentive Plan And Long Term Incentive Plan) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
	Sep. 29, 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	(898)
Canceled, Shares	(29)
Unvested at end of period, Shares	1,136
Shares reserved for future grants	11,833
Unvested at beginning of year, Grant Date Fair Value	$ 46.09
Granted, Grant Date Fair Value	$ 35.76
Vested, Grant Date Fair Value	$ 40.23
Canceled, Grant Date Fair Value	$ 39.85
Unvested at end of period, Grant Date Fair Value	$ 40.86
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 end of period, Shares	72
Shares reserved for future grants	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 end of period, Grant Date Fair Value	$ 43.72