Condensed Consolidating Information (Details 2) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Condensed Consolidating Financial Statements
Net sales	$ 2,043,455	$ 1,584,164	$ 6,139,155	$ 4,772,753
Costs of goods sold	1,844,212	1,444,632	5,367,772	4,230,755
Gross profit (loss)	199,243	139,532	771,383	541,998
Selling, general and administrative	90,458	70,532	269,053	224,066
Operating income (loss)	108,785	69,000	502,330	317,932
Interest expense, net of capitalized interest	44,702	44,286	132,860	125,249
Other (income) expense, net	(3,523)	(6,215)	(13,835)	(12,817)
Income (loss) before income taxes and equity in net income of subsidiaries	67,606	30,929	383,305	205,500
Income taxes (benefit)	27,749	15,574	143,392	79,959
Net income (loss), including portion attributable to noncontrolling interest	39,857	15,355	239,913	125,541
Net loss attributable to noncontrolling interests	3,447	3,386	8,004	7,376
Net income (loss), attributable to Steel Dynamics, Inc.	43,304	18,741	247,917	132,917
Parent
Condensed Consolidating Financial Statements
Net sales	932,793	707,009	2,798,097	2,160,162
Costs of goods sold	809,684	628,785	2,293,661	1,844,035
Gross profit (loss)	123,109	78,224	504,436	316,127
Selling, general and administrative	37,678	21,294	109,870	74,675
Operating income (loss)	85,431	56,930	394,566	241,452
Interest expense, net of capitalized interest	26,163	26,197	77,984	73,082
Other (income) expense, net	(3,232)	(3,419)	(10,115)	(10,685)
Income (loss) before income taxes and equity in net income of subsidiaries	62,500	34,152	326,697	179,055
Income taxes (benefit)	19,524	17,246	103,264	69,098
Net income (loss), including portion attributable to noncontrolling interest	42,976	16,906	223,433	109,957
Equity in net income of subsidiaries	328	1,835	24,484	22,960
Net income (loss), attributable to Steel Dynamics, Inc.	43,304	18,741	247,917	132,917
Guarantors
Condensed Consolidating Financial Statements
Net sales	2,309,239	1,784,299	6,955,744	5,348,572
Costs of goods sold	2,194,687	1,696,687	6,599,291	5,060,220
Gross profit (loss)	114,552	87,612	356,453	288,352
Selling, general and administrative	53,755	49,906	163,742	150,432
Operating income (loss)	60,797	37,706	192,711	137,920
Interest expense, net of capitalized interest	18,237	17,302	53,763	50,160
Other (income) expense, net	(1,895)	(5,619)	(7,659)	(10,526)
Income (loss) before income taxes and equity in net income of subsidiaries	44,455	26,023	146,607	98,286
Income taxes (benefit)	16,023	9,743	54,695	36,781
Net income (loss), including portion attributable to noncontrolling interest	28,432	16,280	91,912	61,505
Net income (loss), attributable to Steel Dynamics, Inc.	28,432	16,280	91,912	61,505
Combined Non-Guarantors
Condensed Consolidating Financial Statements
Net sales	45,407	25,347	143,872	92,116
Costs of goods sold	60,673	39,466	184,424	123,213
Gross profit (loss)	(15,266)	(14,119)	(40,552)	(31,097)
Selling, general and administrative	2,475	2,000	6,545	6,594
Operating income (loss)	(17,741)	(16,119)	(47,097)	(37,691)
Interest expense, net of capitalized interest	2,343	3,494	7,070	9,029
Other (income) expense, net	(437)	37	(2,123)	575
Income (loss) before income taxes and equity in net income of subsidiaries	(19,647)	(19,650)	(52,044)	(47,295)
Income taxes (benefit)	(247)	(7,587)	(260)	(17,935)
Net income (loss), including portion attributable to noncontrolling interest	(19,400)	(12,063)	(51,784)	(29,360)
Net loss attributable to noncontrolling interests	3,447	3,386	8,004	7,376
Net income (loss), attributable to Steel Dynamics, Inc.	(15,953)	(8,677)	(43,780)	(21,984)
Consolidating Adjustments
Condensed Consolidating Financial Statements
Net sales	(1,243,984)	(932,491)	(3,758,558)	(2,828,097)
Costs of goods sold	(1,220,832)	(920,306)	(3,709,604)	(2,796,713)
Gross profit (loss)	(23,152)	(12,185)	(48,954)	(31,384)
Selling, general and administrative	(3,450)	(2,668)	(11,104)	(7,635)
Operating income (loss)	(19,702)	(9,517)	(37,850)	(23,749)
Interest expense, net of capitalized interest	(2,041)	(2,707)	(5,957)	(7,022)
Other (income) expense, net	2,041	2,786	6,062	7,819
Income (loss) before income taxes and equity in net income of subsidiaries	(19,702)	(9,596)	(37,955)	(24,546)
Income taxes (benefit)	(7,551)	(3,828)	(14,307)	(7,985)
Net income (loss), including portion attributable to noncontrolling interest	(12,151)	(5,768)	(23,648)	(16,561)
Equity in net income of subsidiaries	(328)	(1,835)	(24,484)	(22,960)
Net income (loss), attributable to Steel Dynamics, Inc.	$ (12,479)	$ (7,603)	$ (48,132)	$ (39,521)