Condensed Consolidating Information (Details 2) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Condensed Financial Statements, Captions
Net sales	$ 2,079,731	$ 1,632,799	$ 4,095,700	$ 3,188,589
Costs of goods sold	1,803,345	1,440,815	3,523,560	2,786,123
Gross profit (loss)	276,386	191,984	572,140	402,466
Selling, general and administrative	88,167	75,349	178,595	153,534
Operating income (loss)	188,219	116,635	393,545	248,932
Interest expense, net of capitalized interest	44,812	43,448	88,158	80,963
Other (income) expense, net	(5,745)	(3,521)	(10,312)	(6,602)
Income (loss) before income taxes and equity in net income of subsidiaries	149,152	76,708	315,699	174,571
Income taxes (benefit)	53,326	29,911	115,643	64,385
Net income (loss), including portion attributable to noncontrolling interest	95,826	46,797	200,056	110,186
Net loss attributable to noncontrolling interests	2,884	2,410	4,557	3,990
Net income (loss), attributable to Steel Dynamics, Inc.	98,710	49,207	204,613	114,176
Parent
Condensed Financial Statements, Captions
Net sales	952,487	726,120	1,865,304	1,453,153
Costs of goods sold	754,436	607,268	1,483,977	1,215,250
Gross profit (loss)	198,051	118,852	381,327	237,903
Selling, general and administrative	35,528	24,490	72,192	53,381
Operating income (loss)	162,523	94,362	309,135	184,522
Interest expense, net of capitalized interest	26,125	25,038	51,821	46,885
Other (income) expense, net	(3,704)	(4,482)	(6,883)	(7,266)
Income (loss) before income taxes and equity in net income of subsidiaries	140,102	73,806	264,197	144,903
Income taxes (benefit)	42,811	27,866	83,740	51,852
Net income (loss), including portion attributable to noncontrolling interest	97,291	45,940	180,457	93,051
Equity in net income of subsidiaries	1,419	3,267	24,156	21,125
Net income (loss), attributable to Steel Dynamics, Inc.	98,710	49,207	204,613	114,176
Guarantors
Condensed Financial Statements, Captions
Net sales	2,344,958	1,831,842	4,646,505	3,564,273
Costs of goods sold	2,239,226	1,740,778	4,404,604	3,363,533
Gross profit (loss)	105,732	91,064	241,901	200,740
Selling, general and administrative	54,094	50,479	109,987	100,526
Operating income (loss)	51,638	40,585	131,914	100,214
Interest expense, net of capitalized interest	18,264	17,677	35,526	32,858
Other (income) expense, net	(3,089)	(2,057)	(5,764)	(4,907)
Income (loss) before income taxes and equity in net income of subsidiaries	36,463	24,965	102,152	72,263
Income taxes (benefit)	13,768	9,465	38,672	27,038
Net income (loss), including portion attributable to noncontrolling interest	22,695	15,500	63,480	45,225
Net income (loss), attributable to Steel Dynamics, Inc.	22,695	15,500	63,480	45,225
Combined Non-Guarantors
Condensed Financial Statements, Captions
Net sales	50,943	35,359	98,465	66,769
Costs of goods sold	66,156	44,291	123,751	83,747
Gross profit (loss)	(15,213)	(8,932)	(25,286)	(16,978)
Selling, general and administrative	1,948	2,247	4,070	4,594
Operating income (loss)	(17,161)	(11,179)	(29,356)	(21,572)
Interest expense, net of capitalized interest	2,413	3,424	4,727	5,535
Other (income) expense, net	(968)	248	(1,686)	538
Income (loss) before income taxes and equity in net income of subsidiaries	(18,606)	(14,851)	(32,397)	(27,645)
Income taxes (benefit)	(56)	(5,552)	(13)	(10,348)
Net income (loss), including portion attributable to noncontrolling interest	(18,550)	(9,299)	(32,384)	(17,297)
Net loss attributable to noncontrolling interests	2,884	2,410	4,557	3,990
Net income (loss), attributable to Steel Dynamics, Inc.	(15,666)	(6,889)	(27,827)	(13,307)
Consolidating Adjustments
Condensed Financial Statements, Captions
Net sales	(1,268,657)	(960,522)	(2,514,574)	(1,895,606)
Costs of goods sold	(1,256,473)	(951,522)	(2,488,772)	(1,876,407)
Gross profit (loss)	(12,184)	(9,000)	(25,802)	(19,199)
Selling, general and administrative	(3,403)	(1,867)	(7,654)	(4,967)
Operating income (loss)	(8,781)	(7,133)	(18,148)	(14,232)
Interest expense, net of capitalized interest	(1,990)	(2,691)	(3,916)	(4,315)
Other (income) expense, net	2,016	2,770	4,021	5,033
Income (loss) before income taxes and equity in net income of subsidiaries	(8,807)	(7,212)	(18,253)	(14,950)
Income taxes (benefit)	(3,197)	(1,868)	(6,756)	(4,157)
Net income (loss), including portion attributable to noncontrolling interest	(5,610)	(5,344)	(11,497)	(10,793)
Equity in net income of subsidiaries	(1,419)	(3,267)	(24,156)	(21,125)
Net income (loss), attributable to Steel Dynamics, Inc.	$ (7,029)	$ (8,611)	$ (35,653)	$ (31,918)