Steel Dynamics (STLD) 10-K 27 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 20, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	STEEL DYNAMICS INC
Entity Central Index Key	1,022,671
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Public Float			$ 5,979
Entity Common Stock, Shares Outstanding		236,071,369

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and equivalents	$ 1,028,649	$ 841,483
Accounts receivable, net	846,415	703,565
Accounts receivable-related parties	22,422	26,219
Inventories	1,519,347	1,275,211
Other current assets	91,509	83,197
Total current assets	3,508,342	2,929,675
Property, plant and equipment, net	2,675,904	2,787,215
Restricted cash	16,939	18,060
Intangible assets, net	256,909	283,977
Goodwill	386,893	393,351
Other assets	10,745	11,454
Total assets	6,855,732	6,423,732
Current liabilities
Accounts payable	473,765	382,126
Accounts payable-related parties	15,683	13,070
Income taxes payable	3,696	5,593
Accrued payroll and benefits	195,909	164,543
Accrued interest	25,533	30,295
Accrued expenses	125,138	113,556
Current maturities of long-term debt	28,795	3,632
Total current liabilities	868,519	712,815
Long-term debt	2,353,145	2,353,194
Deferred income taxes	305,949	448,375
Other liabilities	21,811	20,649
Total liabilities	3,549,424	3,535,033
Commitments and contingencies
Redeemable noncontrolling interests	111,240	111,240
Equity
Common stock voting, $.0025 par value; 900,000,000 shares authorized 264,135,545 and 264,130,544 shares issued; and 242,110,745 and 243,785,485 shares outstanding, as of March 31, 2017 and December 31, 2016, respectively	644	641
Treasury stock, at cost; 22,024,800 and 20,345,059 shares, as of March 31, 2017 and December 31, 2016 respectively	(665,297)	(416,829)
Additional paid-in capital	1,141,534	1,132,749
Retained earnings	2,874,693	2,210,459
Total Steel Dynamics, Inc. equity	3,351,574	2,927,020
Noncontrolling interests	(156,506)	(149,561)
Total equity	3,195,068	2,777,459
Total liabilities and equity	$ 6,855,732	$ 6,423,732

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
CONSOLIDATED BALANCE SHEETS
Allowance for Doubtful Accounts Receivable, Current	$ 15,036	$ 14,413
Finite-Lived Intangible Assets, Accumulated Amortization	$ 269,868	$ 294,676
Common stock voting, par value (in dollars per share)	$ 0.0025	$ 0.0025
Common stock voting, shares authorized (in shares)	900,000,000	900,000,000
Common stock voting, shares issued (in shares)	265,003,133	264,130,544
Common stock voting, shares outstanding (in shares)	237,396,839	243,785,485
Treasury stock, shares (in shares)	27,606,294	20,345,059

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net sales
Unrelated parties	$ 9,364,213	$ 7,607,180	$ 7,407,233
Related parties	174,584	169,929	187,178
Total net sales	9,538,797	7,777,109	7,594,411
Costs of goods sold	7,956,783	6,442,245	6,862,693
Gross profit	1,582,014	1,334,864	731,718
Selling, general and administrative expenses	394,631	374,009	328,758
Profit sharing	91,309	71,285	23,064
Amortization of intangible assets	29,193	28,765	24,180
Asset impairment charges		132,839	428,500
Operating income	1,066,881	727,966	(72,784)
Interest expense, net of capitalized interest	134,399	146,037	153,950
Other expense (income), net	(2,753)	17,796	15,383
Income before income taxes	935,235	564,133	(242,117)
Income tax expense	129,439	204,127	(96,947)
Net income	805,796	360,006	(145,170)
Net loss attributable to noncontrolling interests	6,945	22,109	14,859
Net income attributable to Steel Dynamics, Inc.	$ 812,741	$ 382,115	$ (130,311)
Basic earnings per share attributable to Steel Dynamics, Inc. stockholders	$ 3.38	$ 1.57	$ (0.54)
Weighted average common shares outstanding - basic (in shares)	240,132	243,576	242,017
Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 3.36	$ 1.56	$ (0.54)
Weighted average common shares and share equivalents outstanding (in shares)	241,781	245,298	242,017
Dividends declared per share (in dollars per share)	$ 0.62	$ 0.56	$ 0.55

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Noncontrolling Interests	Redeemable Noncontrolling Interest	Total
Balances at Dec. 31, 2014	$ 635	$ (398,898)	$ 1,083,435	$ 2,227,843	$ (117,488)	$ 126,340	$ 2,795,527
Common Stock, Shares, Outstanding, Beginning Balance at Dec. 31, 2014	241,449,000
Treasury Stock, Shares, Beginning Balance at Dec. 31, 2014		19,971,000
Proceeds from exercise of stock options, including related tax effect	$ 1	$ (211)	10,975				10,765
Proceeds from exercise of stock options, including related tax effect (in shares)	737,000	10,000
Dividends declared				(133,227)			(133,227)
Noncontrolling investors, net				1,082	(2,269)		(1,187)
Equity-based compensation	$ 2	$ 2,654	15,843	(96)			18,403
Equity-based compensation (in shares)	904,000	(133,000)
Comprehensive and net income (loss)				(130,311)	(14,859)		(145,170)
Balances at Dec. 31, 2015	$ 638	$ (396,455)	1,110,253	1,965,291	(134,616)	126,340	2,545,111
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2015	243,090,000
Treasury Stock, Shares, Ending Balance at Dec. 31, 2015		19,848,000
Proceeds from exercise of stock options, including related tax effect	$ 3		9,834				9,837
Proceeds from exercise of stock options, including related tax effect (in shares)	556,000	12,000
Dividends declared				(136,472)			(136,472)
Noncontrolling investors, net				(356)	7,164	(15,100)	6,808
Share repurchases		$ (25,034)					$ (25,034)
Share repurchases (in shares)	(732,000)	732,000					732,000
Equity-based compensation		$ 4,660	12,662	(119)			$ 17,203
Equity-based compensation (in shares)	871,000	(247,000)
Comprehensive and net income (loss)				382,115	(22,109)		360,006
Balances at Dec. 31, 2016	$ 641	$ (416,829)	1,132,749	2,210,459	(149,561)	111,240	$ 2,777,459
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2016	243,785,000						243,785,485
Treasury Stock, Shares, Ending Balance at Dec. 31, 2016		20,345,000					20,345,059
Dividends declared				(148,231)			$ (148,231)
Share repurchases		$ (252,242)					$ (252,242)
Share repurchases (in shares)	(7,439,000)	7,439,000					7,400,000
Equity-based compensation	$ 3	$ 3,774	8,785	(276)			$ 12,286
Equity-based compensation (in shares)	1,051,000	(178,000)
Comprehensive and net income (loss)				812,741	(6,945)		805,796
Balances at Dec. 31, 2017	$ 644	$ (665,297)	$ 1,141,534	$ 2,874,693	$ (156,506)	$ 111,240	$ 3,195,068
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2017	237,397,000						237,396,839
Treasury Stock, Shares, Ending Balance at Dec. 31, 2017		27,606,000					27,606,294

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 805,796	$ 360,006	$ (145,170)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	298,999	296,109	294,595
Impairment charges		132,839	428,500
Equity-based compensation	36,197	31,656	30,181
Deferred income taxes	(135,899)	53,846	(99,323)
Other adjustments	14,068	20,676	19,886
Changes in certain assets and liabilities:
Accounts receivable	(139,054)	(106,617)	311,302
Inventories	(242,883)	(115,575)	488,003
Other assets	4,188	12,053	(450)
Accounts payable	96,062	106,521	(227,092)
Income taxes receivable/payable	(33,889)	(13,921)	12,706
Accrued expenses	36,021	75,176	(59,513)
Net cash provided by operating activities	739,606	852,769	1,053,625
Investing activities:
Purchases of property, plant and equipment	(164,935)	(198,160)	(114,501)
Acquisition of business, net of cash acquired	(6,192)	(123,351)	(45,000)
Other investing activities	32,022	8,618	16,874
Net cash used in investing activities	(139,105)	(312,893)	(142,627)
Financing activities:
Issuance of current and long-term debt	620,041	473,903	207,930
Repayment of current and long-term debt	(609,914)	(728,993)	(625,924)
Dividends paid	(145,565)	(135,767)	(127,569)
Proceeds from exercise of stock options, including related tax effect		9,564	10,781
Purchases of treasury stock	(252,242)	(25,034)
Other financing activities	(25,655)	(19,098)	(10,547)
Net cash used in financing activities	(413,335)	(425,425)	(545,329)
Increase in cash and equivalents	187,166	114,451	365,669
Cash and equivalents at beginning of period	841,483	727,032	361,363
Cash and equivalents at end of period	1,028,649	841,483	727,032
Supplemental disclosure information:
Cash paid for interest	135,381	150,679	160,190
Cash paid for income taxes, net	$ 296,493	$ 159,950	$ (9,898)

Description of the Business and

Description of the Business and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Description of the Business and Significant Accounting Policies
Description of the Business and Significant Accounting Policies	 Note 1 . D escription of the Business and Summary of Significant Accounting Policies  Description of the Business Steel Dynamics, Inc. (SDI), together with its subsidiaries (the company), is a domestic manufacturer of steel products and metals recycler. The company has three reporting segments: steel operations, metals recycling operations, and steel fabrication operations. Approximately 9% of the company’s workforce in five locations is represented by collective bargaining agreements, and agreements affecting 0.4% of the company’s employees at one location expire during 2018. Steel Operations Segment Steel operations include the company’s Butler Flat Roll Division, Columbus Flat Roll Division, The Techs galvanizing lines, Structural and Rail Division, Engineered Bar Products Division, Vulcan Threaded Products, Inc. (Vulcan) – acquired August 1, 2016, Roanoke Bar Division, Steel of West Virginia, and Iron Dynamics (IDI), a liquid pig iron (scrap substitute) production facility that supplies solely the Butler Flat Roll Division. These operations include electric arc furnace steel mills, producing steel from ferrous scrap and scrap substitutes, utilizing continuous casting, automated rolling mills, with several downstream coating and bar processing lines. Steel operations accounted for 72% of the company’s consolidated net sales during 2017 a nd 2016, and 69% in 2015 . Metals Recycling Operations Segment Metals recycling operations consists solely of OmniSource Corporation (OmniSource), and includes both ferrous and nonferrous processing, transportation, marketing, brokerage, and scrap management services . Metals recycling operations accounted for 15% of the company’s consolidated net sales during 2017 and 2016 and 19% in 2015 . Steel Fabrication Operations Segment Steel fabrication operations include the company’s New Millennium Building Systems’ joist and deck plants located throughout the United States, and in Northern Mexico. Revenues from these plants are generated from the fabrication of trusses, girders, steel joists and steel deck used within the non-residential construction industry. Steel fabrication operations accounted for 9% of the company’s consolidated net sales during 2017, 2016 , and 2015 . Other Other operations consists of subsidiary operations that are below the quantitative thresholds required for reportable segments and primarily consist of our Minnesota ironmaking operations that have been idle since May 2015, and other smaller joint ventures. Also included in “Other” are certain unallocated corporate accounts, such as the company’s senior secured credit facility, senior notes, certain other investments and certain profit sharing expenses.  Our idle Minnesota ironmaking operations consist of Mesabi Nugget, (owned 83% by us); our wholly-owned iron concentrate and potential future iron mining operations, Mesabi Mining; and our wholly-owned (as of December 31, 2016) iron tailings operations, Mining Resources. As of December 31, 2016, the company acquired all $15.1 million of the Mining Resources noncontrolling investor’s redeemable noncontrolling units for cancellation and discharge of all obligations owed to Mining Resources and termination of all existing agreements with the noncontrolling investor. Prior to this transaction, the company owned 82% of Mining Resources. Summary of Significant Accounting Policies Principles of Consolidation The consolidated financial statements include the accounts of SDI, together with its wholly- and majority-owned or controlled subsidiaries, after elimination of intercompany accounts and transactions. Noncontrolling interests represent the noncontrolling owner’s proportionate share in the equity, income, or losses of the company’s majority-owned or controlled consolidated subsidiaries. Use of Estimates These consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States, and accordingly, include amounts that require management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and in the notes thereto. Significant items subject to such estimates and assumptions include the carrying value of property, plant and equipment, intangible assets, and goodwill; valuation allowances for trade receivables, inventories and deferred income tax assets; unrecognized tax benefits; potential environmental liabilities; and litigation claims and settlements. Actual results may differ from these estimates and assumptions. Note 1. Description of the Business and Summary of Significant Accounting Policies (Continued) Revenue Recognition and Allowances for Doubtful Accounts  Except for the steel fabrication operations, the company recognizes revenues from sales and the allowance for estimated returns and claims from these sales at the time the title of the product transfers, upon shipment. Provision is made for estimated product returns and customer claims based on historical experience. If the historical data used in the estimates does not reflect future returns and claims trends, additional provision may be necessary. The company’s steel fabrication operations recognize revenues utilizing a percentage of completion methodology based on steel tons used on completed units to date as a percentage of estimated total steel tons required for each contract. The allowance for doubtful accounts for all operating segments is based on the company’s best estimate of probable credit losses, along with historical experience.  Cash and Equivalents Cash and equivalents include all highly liquid investments with a maturity of three months or less at the date of acquisition. Restricted cash is primarily funds held in escrow as required by various insurance and government organizations.  Inventories Inventories are stated at lower of cost or net realizable value. Cost is determined using a weighted average cost method for raw materials and supplies, and on a first-in, first-out basis for other inventory . Inventory consisted of the following at December 31 (in thousands):     2017 2016  Raw materials $ 675,715 $ 515,924  Supplies 374,515 383,134  Work in progress 128,565 103,606  Finished goods 340,552 272,547  Total inventories $ 1,519,347 $ 1,275,211  Property, Plant and Equipment Property, plant and equipment are stated at cost, which includes capitalized interest on construction in progress amounts, and is reduced by proceeds received from certain state and local government grants and other capital cost reimbursements. The company assigns each fixed asset a useful life ranging from 3 to 20 years for plant, machinery and equipment, and 10 to 40 years for buildings and improvements. Repairs and maintenance are expensed as incurred. Depreciation is provided utilizing the straight-line depreciation methodology, or the units-of-production depreciation methodology for certain production related assets, based on units produced, subject to a minimum and maximum level. Depreciation expense was $263.7 million, $260.6 million, and $263.2 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. Refer to Impairment of Long-Lived Tangible and Definite-Lived Intangible Assets below in Note 1 for discussions regarding the impairments of various property, plant and equipment in 2016 and 2015 .  The company’s property, plant and equipment consisted of the following at December 31 (in thousands):      2017 2016  Land and improvements $ 314,854 $ 311,005  Buildings and improvements 723,504 709,809  Plant, machinery and equipment 4,035,717 3,975,560  Construction in progress 91,433 70,615  5,165,508 5,066,989  Less accumulated depreciation 2,489,604 2,279,774  Property, plant and equipment, net $ 2,675,904 $ 2,787,215        Note 1. Description of the Business and Summary of Significant Accounting Policies (Continued) Intangible Assets The company’s intangible assets consisted of the following at December 31 (in thousands):    Weighted  Average  Useful Amortization  2017 2016 Life Period  Customer and scrap generator relationships $ 394,062 $ 446,688 5 to 25 years 21 years  Trade names 130,550 130,550 15 to 25 years 18 years  Other 2,165 1,415 3 to 5 years 4 years  526,777 578,653 20 years  Less accumulated amortization 269,868 294,676  $ 256,909 $ 283,977  The company utilizes an accelerated amortization methodology for customer and scrap generator relationships in order to follow the pattern in which the economic benefits of the amounts are anticipated to be consumed. Trade names are amortized using a straight-line methodology. Amortization of intangible assets was $29.2 million, $28.8 million, and $24.2 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively . Estimated amortization expense related to amortizable intangibles for the years ending December 31 is as follows (in thousands):     2018 $ 26,910  2019 24,823  2020 22,629  2021 20,840  2022 19,231  Thereafter 142,476  Total $ 256,909  Impairment of Long-Lived Tangible and Definite ‑Lived Intangible Assets The company reviews long-lived assets for impairment whenever events or changes in circumstances indicate the carrying amount of such assets may not be fully recoverable. Impairment losses are recorded on long-lived assets used in operations when indicators of impairment are present and the undiscounted cash flows estimated to be generated by those assets are less than the assets’ carrying amounts. The impairment loss is measured by comparing the fair value of the assets to its carrying amount. The company considers various factors and determines whether an impairment test is necessary, including by way of examples, a significant and prolonged deterioration in operating results and/or projected cash flows, significant changes in the extent or manner in which an asset is used, technological advances with respect to assets which would potentially render them obsolete, our strategy and capital planning, and the economic climate in markets to be served.  A long-lived asset is classified as held for sale upon meeting specified criteria related to ability and intent to sell. An asset classified as held for sale is measured at the lower of its carrying amount or fair value less cost to sell. As of December 31, 2017 and 2016, the company reported $8.7 and $29.3 million, respectively, of assets held for sale within other current assets in our consolidated balance sheet. An impairment loss is recognized for any initial or subsequent write-down of the asset held for sale to its fair value less cost to sell. For assets determined to be classified as held for sale in the year ended December 31, 2017 and 2016, the asset carrying amounts approximated their fair value less cost to sell. The company recorded a $10.3 million asset impairment charge in the consolidated statement of operations for assets determined to be classified as held for sale in the year ended December 31, 2015. The company determined fair value using Level 3 fair value inputs as provided for under ASC 820, consisting of information provided by brokers and other external sources along with management’s own assumptions.  Significant events occurred during the fourth quarter of 2016, including the previously noted termination of all existing agreements with the Mining Resources noncontrolling investor, that represented impairment indicators related primarily to Mining Resources and Mesabi Mining fixed assets within our Minnesota ironmaking operations. The company therefore undertook a fourth quarter 2016 assessment of the recoverability of the carrying amounts of primarily our Mining Resources and Mesabi Mining operation’s fixed assets. With the company’s outlook at the time of this 2016 assessment regarding future cash flows, the company concluded that the carrying amounts of the fixed assets were no longer fully recoverable, and they were in fact impaired. This 2016 assessment resulted in a non-cash asset impairment charge of $127.3 million, including amounts attributable to noncontrolling interests of $13.1 million, which reduced net income attributable to Steel Dynamics, Inc. by $72.9 million for the year ended December 31, 2016. The carrying values of the impaired assets were adjusted to their estimated fair values at that time as determined primarily on the cost approach, as well as expected future discounted cash flows (an income approach), using Level 3 fair value inputs as provided for under ASC 820. Note 1. Description of the Business and Summary of Significant Accounting Policies (Continued) Goodwill The company’s goodwill is allocated to the following reporting units at December 31 (in thousands):   2017 2016  Steel Operations Segment  Columbus Flat Roll Division $ 19,682 $ 19,682  The Techs 142,783 142,783  Vulcan Threaded Products 7,824 7,824  Roanoke Bar Division 29,041 29,041  Metals Recycling Operations Segment  OmniSource 90,638 97,096  Indiana Steel Mills 95,000 95,000  Steel Fabrication Operations Segment – New Millennium Building Systems 1,925 1,925  $ 386,893 $ 393,351  OmniSource goodwill decreased $6.5 million in 2017 in recognition of the 2017 tax benefit related to the normal amortization of the component of OmniSource tax-deductible goodwill in excess of book goodwill. In 2016, a $5.5 million OmniSource goodwill impairment charge was recorded in conjunction with OmniSource entering into a definitive sale agreement with a third-party pertaining to certain OmniSource long-lived assets (classified and reported as held for sale as of December 31, 2016), inventory and spare parts, as provided under ASC 350. In 2015, a $341.3 million OmniSource goodwill impairment charge was recorded pursuant to the company’s annual review for impairment of goodwill and indefinite-lived intangible assets, as discussed further under “Impairment of Goodwill and Indefinite-Lived Intangible Assets” below. Cumulative OmniSource goodwill impairment charges were $346.8 million at December 31, 2017 and 2016.  Impairment of Goodwill and Indefinite ‑Lived Intangible Assets At least once annually (as of October 1) or when indicators of impairment exist, the company performs an impairment test for goodwill. Goodwill is allocated to various reporting units, which are generally one level below the company’s operating segments. The company utilizes a two-stepped approach to evaluate goodwill impairment. The first step of the test determines if there is potential goodwill impairment. In this step, the company compares the fair value of the reporting unit to its carrying amount (which includes goodwill). The fair value of the reporting unit is determined by using an estimate of future cash flows utilizing a risk-adjusted discount rate to calculate the net present value of future cash flows (income approach), and by using a market approach based upon an analysis of valuation metrics of comparable peer companies, using Level 3 fair value inputs as provided for under ASC 820. If the fair value exceeds the carrying value, there is no impairment. If the carrying amount exceeds the fair value, the company performs the second step of the test, which measures the amount of impairment loss to be recorded. In the second step, the company compares the carrying amount of the goodwill to the implied fair value of the goodwill based on the net fair value of the recognized and unrecognized assets and liabilities of the reporting unit to which it is allocated. If the implied fair value is less than the carrying value, an impairment loss is recorded to the extent that the fair value of the goodwill is less than its carrying value. At least once annually (as of October 1) or when indicators of impairment exist, the company tests indefinite-lived intangible assets for impairment through the comparison of the fair value of the specific intangible asset with its carrying amount. The fair value of the intangible asset is determined by using an estimate of future cash flows attributable to the asset and a risk-adjusted discount rate to compute a net present value of future cash flows (income approach). If the fair value is less than the carrying value, an impairment loss is recorded in an amount equal to the excess in carrying value. During the company’s 2015 annual goodwill and indefinite-lived intangible asset impairment analysis, the company determined that the fair value of OmniSource was less than its carrying value, and upon the completion of the second step of the impairment analysis, that the goodwill and trade name indefinite-lived intangible assets were impaired. The OmniSource goodwill and trade name indefinite-lived intangible assets were written down to their respective fair values at that time, resulting in non-cash asset impairment charge of $341.3 million and $68.5 million, respectively, that are reflected in asset impairment charge in the consolidated statement of operations for the year ended December 31, 2015, within the metals recycling operations. No impairment was identified during the company’s 2017 and 2016 annual goodwill and indefinite-lived intangible asset impairment analysis. Equity ‑Based Compensation The company has several stock ‑based employee compensation plans which are more fully described in Note 6 Equity-Based Incentive Plans . Compensation expense for restricted stock units, deferred stock units, restricted stock, and performance awards is recorded over the vesting periods using the fair value as determined by the closing fair market value of the company’s common stock on the grant date, and with respect to performance awards, an estimate of probability of award achievement during the performance period. The company recognizes forfeitures as they Note 1. Description of the Business and Summary of Significant Accounting Policies (Continued) occur. Compensation expense for these stock ‑based employee compensation plans was $36.6 million, $30.4 million, and $27.1 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. Income Taxes The company accounts for income taxes and the related accounts under the liability method. Deferred tax liabilities and assets are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted rates expected to be in effect during the year in which the basis differences reverse. Earnings Per Share Basic earnings per share is based on the weighted average shares of common stock outstanding during the period. Diluted earnings per share assumes the weighted average dilutive effect of common share equivalents outstanding during the period applied to the company’s basic earnings per share. Common share equivalents represent potentially dilutive restricted stock units, deferred stock units, restricted stock, and performance awards, and are excluded from the computation in periods in which they have an anti-dilutive effect. There were no anti-dilutive common stock equivalents as of and for the years ended December 31, 2017 and 2016 . There were 1.5 million anti-dilutive common stock equivalents as of and for the year ended December 31, 2015 . The following table presents a reconciliation of the numerators and the denominators of the company’s basic and diluted earnings per share computations for the years ended December 31 (in thousands, except per share data):      2017 2016  Net Income Shares Per Share Net Income Shares Per Share  (Numerator) (Denominator) Amount (Numerator) (Denominator) Amount  Basic earnings per share $ 812,741 240,132 $ 3.38 $ 382,115 243,576 $ 1.57  Dilutive common share equivalents - 1,649 - 1,722  Diluted earnings per share $ 812,741 241,781 $ 3.36 $ 382,115 245,298 $ 1.56     2015  Net Loss Shares Per Share  (Numerator) (Denominator) Amount  Basic earnings per share $ (130,311) 242,017 $ (0.54)  Dilutive common share equivalents - -  Diluted earnings per share $ (130,311) 242,017 $ (0.54)   Concentration of Credit Risk Financial instruments that potentially subject the company to significant concentrations of credit risk principally consist of temporary cash investments and accounts receivable. The company places its temporary cash investments with high credit quality financial institutions and companies, and limits the amount of credit exposure from any one entity. The company is exposed to credit risk in the event of nonpayment by customers. The company mitigates its exposure to credit risk, which it generally extends initially on an unsecured basis, by performing ongoing credit evaluations and taking further action if necessary, such as requiring letters of credit or other security interests to support the customer receivable. Management’s estimation of the allowance for doubtful accounts is based upon known credit risks, historical loss experience and current economic conditions affecting the company’s customers. Customer accounts receivable are charged off when all collection efforts have been exhausted and the amounts are deemed uncollectible. Heidtman Steel Products (Heidtman), a related party, accounted for 2% and 3% of the company’s net accounts receivable at December 31, 2017 , and December 31, 2016 . Derivative Financial Instruments The company recognizes all derivatives as either assets or liabilities in the consolidated balance sheets and measures those instruments at fair value. Derivatives that are not designated as hedges must be adjusted to fair value through earnings. Changes in the fair value of derivatives that are designated as hedges, depending on the nature of the hedge, are recognized as either an offset against the change in fair value of the hedged balance sheet item in the case of fair value hedges or as other comprehensive income in the case of cash flow hedges, until the hedged item is recognized in earnings. The ineffective portion of a derivative’s change in fair value is immediately recognized in earnings. The company offsets fair value amounts recognized for derivative instruments executed with the same counterparty under master netting agreements. Note 1. Description of the Business and Summary of Significant Accounting Policies (Continued) In the normal course of business, the company has derivative financial instruments in the form of forward contracts in various commodities, may have involvement with derivative financial instruments related to managing fluctuations in foreign exchange rates, and in the past has had derivative financial instruments related to managing fluctuations in interest rates. At the time of acquiring these financial instruments, the company designates and assigns these instruments as hedges of specific assets, liabilities or anticipated transactions. When hedged assets or liabilities are sold or extinguished, or the anticipated transaction being hedged is no longer expected to occur, the company recognizes the gain or loss on the designated hedged financial instrument. The company routinely enters into forward contracts in various commodities, primarily nonferrous metals (specifically aluminum and copper) in our metals recycling operations, to reduce exposure to commodity related price fluctuations. The company does not enter into these derivative financial instruments for speculative purposes. Recently Adopted/Issued Accounting Standards  In May 2014, the FASB issued ASU 2014-09, which is codified in ASC 606, Revenue Recognition – Revenue from Contracts with Customers, which amends the guidance in former ASC 605, Revenue Recognition . FASB has since issued clarifying guidance in the form of ASU 2016-08, Revenue from Contracts with Customers: Principal versus Agent Consideration (Reporting Revenue Gross versus Net) , ASU 2016-10, Revenue from Contract with Customers: Identifying Performance Obligations and Licensing , and ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients, collectively (ASC 606). The core principle of ASC 606 is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASC 606 also requires additional disclosures to help users of financial statements better understand the nature, amount, timing, and potential uncertainty of revenue that is recognized. ASC 606 guidance is effective for annual and interim periods beginning after December 15, 2017, but could have been early adopted for annual and interim periods ending after December 15, 2016, using a full retrospective or modified retrospective approach. The company has completed its adoption plan in which it identified revenue streams, and analyzed those revenue streams, based on a detailed review of its business and contracts, pursuant to the new accounting requirements. The company concluded that there will be no change in the amount or timing of revenue recognized under the new standard, or significant changes required to the company’s functions, processes or systems. The company has adopted ASC 606 in the first quarter of 2018 using the modified retrospective approach. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842): which establishes a new lease accounting model that requires lessees to recognize a right of use asset and related lease liability for most leases having lease terms of more than 12 months (ASU 2016-02). Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. This new guidance is effective for annual and interim periods beginning after December 15, 2018, but can be early adopted. The company is currently evaluating the impact of the provisions of ASU 2016-02, and anticipates adopting on January 1, 2019. 

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Acquisitions
Acquisitions	Note 2. Acquisition  Vulcan Threaded Products, Inc.  In August 2016, the company acquired 100% of Vulcan in Pelham, Alabama, for $113.0 million in cash from available funds. Vulcan is the nation’s largest manufacturer and supplier of threaded rod products, and also produces cold drawn and heat treated bar. The acquisition of Vulcan is consistent with one of our target growth objectives – higher-margin downstream business opportunities that utilize our steel products in their manufacturing processes. Vulcan utilizes special-bar-quality products produced at our Engineered Bar Products Division. Post-closing operating results of Vulcan are reflected in the steel operations reporting segment. 

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2017
Long-Term Debt
Long-Term Debt	Note 3. Long-Term Debt The company’s borrowings consisted of the following at December 31 (in thousands):    2017 2016  5.125% senior notes due 2021 $ 700,000 $ 700,000  5 1 / 4 % senior notes due 2023 400,000 400,000  5.500% senior notes due 2024 500,000 500,000  4.125% senior notes due 2025 350,000 -  5.000% senior notes due 2026 400,000 400,000  6 3 / 8 % senior notes due 2022 - 350,000  Other obligations 58,852 36,791  Total debt 2,408,852 2,386,791  Less debt issuance costs 26,912 29,965  Total amounts outstanding 2,381,940 2,356,826  Less current maturities 28,795 3,632  Long-term debt $ 2,353,145 $ 2,353,194  Financing Activity In September 2017, the company issued $350.0 million of 4.125% senior notes due 2025 (the "2025 Notes"), the proceeds of which, along with available cash, were used to fund the September 2017 tender offer to purchase at a redemption price of 103.563% a total of $182.9 million principal amount, plus accrued and unpaid interest to, but not including, the date of repurchase, of the company's 6.375% senior notes due 2022 (the "2022 Notes"), and the October 2017 call and repayment at a redemption price of 103.188% of the $167.1 million remaining outstanding principal amount of the 2022 Notes, plus accrued and unpaid interest to, but not including, the date of repayment. The company recorded expenses related to tender and call premiums, write off of unamortized debt issuance costs, and other expenses of $14.6 million, which are reflected in other expenses in the consolidated statements of operations for the year ended December 31, 2017.  In December 2016, the company issued $400.0 million of 5.000% senior notes due 2026 (the "2026 Notes"), the proceeds of which, along with available cash, were used to fund the December 2016 tender offer to purchase at a redemption price of 103.388% a total of $266.3 million principal amount, plus accrued and unpaid interest to, but not including, the date of repurchase, of the company's 6.125% senior notes due 2019 (the "2019 Notes"), and the December 2016 call and repayment at a redemption price of 103.063% of the $133.7 million remaining outstanding principal amount of the 2016 Notes plus accrued and unpaid interest to, but not including, the date of repayment. In addition, the company repaid the remaining $228.1 million of outstanding senior secured term loan debt with available cash in December 2016, which was set to mature in November 2019. The company recorded expenses related to tender and call premiums, write off of unamortized debt issuance costs, and other expenses of $16.5 million, which are reflected in other expenses in the consolidated statement of operations for the year ended December 31, 2016. In March 2015, the company called and repaid all $350.0 million of its outstanding 7 5 / 8 % Senior Notes due 2020 (the “2020 Notes”) at a redemption price of 103.813% of the principal amount of the 2020 Notes, plus accrued and unpaid interest to, but not including, the date of redemption. The company recorded expenses related to call premiums, write off of unamortized debt issuance costs, and other expenses of $16.7 million, which are reflected in other expense in the consolidated statement of operations for the year ended December 31, 2015. Senior Secured Credit Facility, due 2019 The company’s November 2014 senior secured credit facility (“Facility”), which provides a $1.2 billion Revolver, matures November 2019. Subject to certain conditions, the company has the opportunity to increase the Revolver size by at least $750.0 million. The Facility is guaranteed by certain of the company’s subsidiaries; and is secured by substantially all of the company’s and its wholly-owned subsidiaries’ receivables and inventories, and by pledges of all shares of the company’s wholly-owned subsidiaries’ capital stock or other equity interests, and intercompany debt held by the company as collateral. The Revolver is available to fund working capital, capital expenditures, and other general corporate purposes. The Facility pricing grid is adjusted quarterly, and is based on the company’s leverage of net debt (as defined in the Facility) to last-twelve-months (LTM) consolidated adjusted EBITDA (earnings before interest, taxes, depreciation, amortization, and certain other non-cash items as allowed in the Facility). The minimum pricing is LIBOR plus 1.00% or Prime, and the maximum pricing is LIBOR plus 2.00% or Prime plus 1.00% . In addition, the company is subject to an unused commitment fee of between 0.225% and 0.375% (based on leverage of net debt to LTM EBITDA) which is applied to the unused portion of the Revolver each quarter. Note 3. Long-Term Debt (Continued) The Facility contains financial covenants and other covenants pertaining to the company’s ability (which may under certain circumstances be limited) to make capital expenditures; incur indebtedness; permit liens on property; enter into transactions with affiliates; make restricted payments or investments; enter into mergers, acquisitions or consolidations; conduct asset sales; pay dividends or distributions, or enter into other specified transactions and activities. The company’s ability to borrow funds within the terms of the Revolver is dependent upon its continued compliance with the financial and other covenants. At December 31, 2017 , the company had $1.2 billion of availability on the Revolver, $11.9 million of outstanding letters of credit and other obligations which reduce availability, and no outstanding borrowings. The financial covenants under the company’s Facility state that it must maintain an interest coverage ratio of not less than 2.50 : 1.00. The company’s interest coverage ratio is calculated by dividing its LTM consolidated adjusted EBITDA by its LTM gross interest expense less amortization of financing fees. In addition, a net debt (as defined in the Facility) to LTM consolidated adjusted EBITDA (net debt leverage ratio) of not more than 5.00 :1.00 must be maintained. If the net debt leverage ratio exceeds 3.50 :1:00 at any time, the company’s ability to make certain payments as defined in the Facility (which includes cash dividends to stockholders and share purchases, among other things), is limited. At December 31, 2017 , the company’s interest coverage ratio and net debt leverage ratio were 10.75 :1.00 and 1.35 :1.00, respectively. The company was therefore in compliance with these covenants at December 31, 2017 , and anticipates remaining in compliance during the next twelve months. Senior Unsecured Notes  We have five different tranches of senior unsecured notes (Notes) outstanding. These Notes are in equal right of payment with all existing and future senior unsecured indebtedness and are senior in right of payment to all subordinated indebtedness. These Notes contain provisions that allow the company to redeem the senior notes on or after the dates and at redemption prices (expressed as a percentage of principal amount) listed below. Additionally, these Notes generally allow the company to redeem some or all of the Notes by paying a “make-whole” premium any time prior to the dates listed below. The company may redeem up to 35% of each of the Notes at a redemption price and by the dates listed below using the proceeds from the sales of the company’s common stock. See the key terms of each of the Notes outstanding below.      Issue 2021 Notes 2023 Notes 2024 Notes 2025 Notes 2026 Notes  Outstanding Balance $700.0 million $400.0 million $500.0 million $350.0 million $400.0 million  Stated Interest Rate 5.125% 5 1 / 4 % 5.500% 4.125% 5.000%  Semi-Annual Interest Payment Dates April 1 and April 15 and April 1 and March 15 and June 15 and  October 1 October 15 October 1 September 15 December 15  Equity Redemption Option Price & Date N/A – date N/A – date N/A – date 104.125% 105.000%  passed passed passed September 15, 2020 December 15, 2019  “Make-Whole” Option Date N/A – date passed April 15, 2018 October 1, 2019 September 15, 2020 December 15, 2021  First Call Price & Date N/A – date 102.625% 102.750% 102.063% 102.500%  passed April 15, 2018 October 1, 2019 September 15, 2020 December 15, 2021  Second Call Price & Date 101.281% 101.750% 101.833% 101.031% 101.667%  October 1, 2018 April 15, 2019 October 1, 2020 September 15, 2021 December 15, 2022  Third Call Price & Date 100.000% 100.875% 100.917% 100.000% 100.833%  October 1, 2019 April 15, 2020 October 1, 2021 September 15, 2022 December 15, 2023  Fourth Call Price & Date - 100.000% 100.000% - 100.000%  April 15, 2021 October 1, 2022 December 15, 2024  Maturity Date October 1, 2021 April 15, 2023 October 1, 2024 September 15, 2025 December 15, 2026   Other Obligations Minnesota Economic Development State Secured Loans . Mesabi Nugget has loans from various Minnesota state agencies related to the construction and ultimate operation of Mesabi Nugget. These loans require monthly principal and interest payments at a 3.5% interest rate until February 2017, and then at 5.0% through maturity in 2027. Amounts due under these loans were $20.6 million and $22.3 million at December 31, 2017 , and 2016 , respectively. Other Secured Loans. One of the company’s controlled subsidiaries entered into financing agreements for certain equipment which bear interest at 6.0% , with monthly principal and interest payments required through maturities in 2027 and 2028. The outstanding principal balance of these agreements was $8.9 million and $9.5 million at December 31, 2017 , and 2016 , respectively.  One of the company’s controlled subsidiaries has a secured credit agreement which provides a revolving variable rate credit facility of up to $40.0 million, subject to a borrowing base determined from eligible accounts receivable and inventory, and other cash flow restrictions. Interest, which was 3.9% at December 31, 2017 , is payable monthly. Amounts due under this credit facility were $25.7 million at December 31, 2017. There were no amounts due under this credit facility at December 31, 2016.  Note 3. Long-Term Debt (Continued) Unsecured Loans. The company has an unsecured electricity transmission facility loan which bears interest at 8.1% , with monthly principal and interest payments required through maturity in 2022. The company has an unused $3.0 million stand-by letter of credit in conjunction with this loan. The outstanding principal balance was $3.6 million and $4.2 million as of December 31, 2017 , and 2016 , respectively.  Outstanding Debt Maturities Maturities of outstanding debt as of December 31, 2017 , are as follows (in thousands):    2018 $ 28,795  2019 3,291  2020 3,492  2021 703,708  2022 3,174  Thereafter 1,666,392  $ 2,408,852  The company capitalizes interest on all qualifying construction in progress assets. For the years ended December 31, 2017 , 2016 , and 2015 , total interest costs incurred were $136.1 million, $148.5 million, and $154.4 million, respectively, of which $1.7 million, $2.5 million and $457,000 , respectively, were capitalized.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Taxes
Income Taxes	Note 4. Income Taxes The company files a consolidated federal income tax return. The current and deferred federal and state income tax expense (benefit) for the years ended December 31 is as follows (in thousands):    2017 2016 2015  Current income tax expense $ 269,387 $ 153,176 $ 6,391  Deferred income tax expense (benefit) (139,948) 50,951 (103,338)  Total income tax expense (benefit) $ 129,439 $ 204,127 $ (96,947)  A reconciliation of the statutory rates to the actual effective tax rates for the years ended December 31 are as follows:    2017 2016 2015  Statutory federal tax rate 35.0 % 35.0 % 35.0 %  Impact from Tax Reform (19.3) - -  State income taxes, net of federal benefit 1.4 2.6 6.3  Domestic manufacturing deduction (2.6) (2.5) -  Noncontrolling interests 0.3 1.4 (2.1)  Tax benefit of equity compensation (1.1) (1.0) 0.4  Other permanent differences 0.1 0.7 0.4  Effective tax rate 13.8 % 36.2 % 40.0 %  On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act of 2017 (the “TCJA Act”) which, among other provisions, reduces the corporate income tax rate from 35% to 21% , effective January 1, 2018. The TCJA Act also includes a one-time transition tax related to cumulative foreign earnings, as the United States transitions from a worldwide tax system to a territorial tax system. During the fourth quarter of 2017, the company recorded a $180.6 million net tax benefit to reflect the impacts of the TCJA Act, including a $182.5 million tax benefit to revalue its net deferred tax assets and liabilities as of December 31, 2017, using the newly enacted rate, partially offset by tax expense of $1.9 million related to the transition tax on cumulative foreign earnings. While the company believes the $180.6 million tax benefit is a reasonable estimate of the impact of the TCJA Act, additional guidance and clarifications of the TCJA Act are expected to be provided in the future. Although the company does not anticipate any material adjustments, future tax expense or benefit related to the TCJA Act may need to be recorded as additional guidance and clarifications of the TCJA Act are provided. Once the company finalizes certain tax positions when it files its 2017 US tax return, it will conclude whether any further adjustments are necessary and record the amounts as a component of tax expense (benefit) in the reporting period in which such adjustments are determined, which will be no later than the fourth quarter 2018.  Note 4. Income Taxes (Continued) Significant components of the company’s deferred tax assets and liabilities at December 31 are as follows (in thousands):     2017 2016  Deferred tax assets  Accrued expenses and allowances $ 16,322 $ 24,986  Inventories 4,109 11,805  Net operating loss carryforwards 33,693 48,920  Intangible assets - 14,779  Other 8,074 8,491  62,198 108,981  Less: valuation allowance (20,714) (33,427)  Total net deferred tax assets 41,484 75,554   Deferred tax liabilities  Property, plant and equipment (344,511) (519,977)  Intangible assets (1,292) -  Other (1,630) (3,952)  Total deferred tax liabilities (347,433) (523,929)  Net deferred tax liability $ (305,949) $ (448,375)  Certain wholly-owned and controlled subsidiaries of the company file separate federal and state income tax returns. These subsidiaries have generated federal net operating loss carryforwards of $93.2 million which expire in 2032 to 2037, and state net operating loss carryforwards which principally expire in the years 2025 to 2037. Management has considered the scheduled reversal of the deferred tax liabilities, historical taxable losses, projected taxable income and tax planning strategies in determining that it is more likely than not that some of the deferred tax assets relating to the tax loss carryforwards of the subsidiaries will not be realized. Based on these evaluations, valuation allowances of $20.7 million and $33.4 million have been recorded as of December 31, 2017, and 2016, respectively. The $12.7 million decrease in valuation allowance in the year ended December 31, 2017, primarily relates to the change in future value due to the TCJA Act and the release of a valuation allowance in the amount of $4.3 million for certain state net operating loss carryforwards. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):     2017 2016 2015  Balance at January 1 $ 19,107 $ 15,991 $ 17,338  Increases related to current year tax positions 300 300 -  Increases related to prior year tax positions 271 5,452 81  Decreases related to prior year tax positions (863) (535) (719)  Settlements with taxing authorities (2,066) (2,101) (70)  Lapses in statute of limitations - - (639)  Balance at December 31 $ 16,749 $ 19,107 $ 15,991  Included in the balance of unrecognized tax benefits at December 31, 2017, are potential benefits of $12.5 million that, if recognized, would affect the effective tax rate. The company recognizes interest and penalties related to its tax contingencies on a net-of-tax basis in income tax expense. During the year ended December 31, 2017, the company recognized expense from the increase of interest expense of $85,000 , net of tax. In addition to the unrecognized tax benefits in the table above, the company had $4.8 million accrued for the payment of interest and penalties at December 31, 2017.    Note 4. Income Taxes (Continued) The company files income tax returns in the United States federal jurisdiction as well as income tax returns in various state jurisdictions. The company is subject to examination and proposed adjustments by the IRS for the calendar year 2010 and thereafter. At this time the company does not believe there will be any significant examination adjustments that would result in a material change to the company’s financial position, results of operations or cash flows. It is reasonably possible that the amount of unrecognized tax benefits could change in the next twelve months as a result of these federal income tax audits, and other state income tax audits. Based on the current audits in process, the payment of taxes as a result of audit settlements could be in an amount from zero to $3.3 million by the end of 2018. With the exception of the 2010 and 2011 federal returns, the company is no longer subject to federal, state and local income tax examinations by tax authorities for years ended before 2012.

Shareholders_ Equity

Shareholders’ Equity	12 Months Ended
	Dec. 31, 2017
Shareholders’ Equity
Changes in Equity	Note 5. Shareholders’ Equity Cash Dividends The company declared cash dividends of $148.2 million , or $0.62 per common share, during 2017 ; $136.5 million , or $0.56 per common share, during 2016 ; and $133.2 million , or $0.55 per common share, during 2015 . The company paid cash dividends of $145.6 million , $135.8 million and $127.6 million during 2017 , 2016 , and 2015 , respectively. Treasury Stock During 2016, the company’s board of directors authorized a share repurchase program of up to $450.0 million of the company’s common stock in open market or private transactions, cancelling the previously authorized program. The share repurchase program does not require the company to acquire any specific number of shares and may be modified, suspended, extended or terminated by the company. The company repurchased 7.4 million shares for $252.2 million during 2017 , and 732,000 shares for $25.0 million during 2016 . At December 31, 2017 , the company had remaining authorization to repurchase $172.7 million of additional shares. The share repurchase program does not have an expiration date.

Equity-based Incentive Plans

Equity-based Incentive Plans	12 Months Ended
	Dec. 31, 2017
Equity-based Incentive Plans [Abstract]
Equity-based Incentive Plans	Note 6. Equity ‑Based Incentive Plans 2015 Equity Incentive Plan (2015 Plan)  The 2015 Plan is designed to attract, motivate and retain qualified persons that are able to make important contributions to the company’s success. To accomplish these objectives, the 2015 Plan provides for awards of equity ‑based incentives through granting of restricted stock units (RSUs), deferred stock units (DSUs), restricted stock awards, stock options, unrestricted stock awards, stock appreciation rights (SARs), and performance awards, such as long-term incentive compensation program (LTIP). The company’s stockholders approved the 2015 Plan in May 2015, and 12.5 million shares of common stock were reserved for issuance upon exercise of equity grants through December 31, 2025. The 2015 Plan uses a fungible share concept under which any awards that are not a full-value award, such as stock options and SARs, will be counted against the share limit as one share for each share of common stock, and awards that are full-value awards, such as RSUs, DSUs, restricted and unrestricted stock awards, and performance awards, will be counted against the share limit as 2.09 shares for each share of common stock. At December 31, 2017 , there were 5.3 million shares in the fungible share reserve still available for issuance. Substantially all of the company’s employees receive RSUs, which are granted annually in November at no cost to employees, vest 100% over the shorter of two years from grant date or upon the recipient reaching retirement eligible age ( 59 ½ years), and the stock is issued to employees upon vesting. The company satisfies RSUs with newly issued shares, and satisfies restricted stock awards, DSUs, and performance awards with treasury shares. In addition to the RSUs and LTIP awards granted during the three year period ended December 31, 2017 , presented below, the company awarded 34,000 , 60,000 and 51,000 DSUs in 2017 , 2016 and 2015 , respectively; and 200,000 and 86,000 SARs in 2017 and 2016, respectively. Note 6. Equity ‑Based Incentive Plans (Continued) Restricted Stock Units  A summary of the company’s RSU activity and outstanding RSUs as of December 31, 2017, are presented below (dollars in thousands except grant date fair value):   Weighted Aggregate  Number Average Grant Intrinsic Unrecognized  of RSUs Date Fair Value Value Compensation  Outstanding RSUs as of January 1, 2015 2,011,226 $19.85 $ 39,702 $ 25,171  Granted 1,589,309 $16.70  Vested (1,197,403) $18.13  Forfeited (124,428) $19.89  As of December 31, 2015 2,278,704 $18.55 $ 40,720 $ 27,615  Granted 852,063 $32.40  Vested (962,828) $22.76  Forfeited (139,922) $18.50  As of December 31, 2016 2,028,017 $22.38 $ 72,157 $ 29,086  Granted 828,955 $36.29  Vested (1,364,593) $18.50  Forfeited (78,737) $23.52  As of December 31, 2017 (nonvested) 1,413,642 $34.22 $ 60,970 $ 32,017  The weighted average remaining life before vesting of the outstanding RSUs as of December 31, 2017 , is 1.37 years. The fair value of RSUs vesting during 2017 , 2016 , and 2015 was $58.8 million, $34.3 million, and $21.4 million, respectively, and was net-share settled such that the company withheld shares with value equivalent to the employees’ minimum statutory obligation for the applicable income and other employment taxes, and remitted the cash to the appropriate taxing authorities. The total shares withheld in 2017 , 2016 , and 2015 were approximately 457,000 , 338,000 , and 427,000 shares, respectively, and were based on the value of the RSUs on their vesting dates as determined by the company’s closing stock price. Stock Options  Prior to 2012, substantially all of the company’s employees were granted stock options at an exercise price of 100% of the fair market value of the company’s common stock on the date of grant, which vested 100% six months after the date of grant, with a maximum term of five years. There have been no stock options granted since 2011, thus the five year maximum term of the 2011 grant has expired, no stock options remain outstanding or exercisable, and there is no unrecognized stock option compensation expense at December 31, 2016 or 2017 . A summary of the company’s stock option activity and certain information concerning the company’s outstanding options are presented below.     Weighted Weighted Average  Number Average Grant Date  of Options Exercise Price Fair Value  Outstanding options as of January 1, 2015 1,398,515 $14.62 $5.61  Exercised (753,159) $14.75 $5.75  Forfeited (49,411) $15.02 $5.87  As of December 31, 2015 595,945 $14.43 $5.41  Exercised (570,197) $14.41 $5.40  Forfeited (25,748) $14.96 $5.62  As of December 31, 2016 and 2017 - N/A N/A  The aggregate intrinsic value of options exercised was $5.6 million and $4.0 million for the years ended December 31, 2016 and 2015 , respectively.  Note 6. Equity ‑Based Incentive Plans (Continued) Long-Term Incentive Compensation Program (LTIP)  The company maintains an LTIP performance-based program directed toward key senior executives of the company, as determined at the discretion of the Compensation Committee of the Board of Directors. Awards are in shares of the company’s common stock using the stock price on the first day of the performance period to convert each key senior executive’s predetermined multiple of annual base salary. The performance period is generally three years; however, certain transition awards were issued in 2013 and 2017 with shorter performance periods. Performance is measured in terms of equal portions of four growth and profitability measures, as compared to the same measures, similarly treated, of a pre-established group of steel sector competitors. Awards earned can range from zero to 100% of the shares awarded. Once earned on the basis of performance, one-third of the shares vest immediately, and the remaining shares vest in equal annual installments over an additional two-year service-based vesting period requirement. The Compensation Committee granted the following three-year performance period awards, and two-year and one-year performance period transition awards, which have been earned and have or will be issued over the vesting period as follows:     Maximum  Shares That Award  Could Be Issued Earned Award Issued/Issuable   2013 LTIP Award:  Two-year performance period transition award 173,319 159,457 53,154 March 2015  66,252 March 2016  40,051 March 2017   Three-year performance period award 173,319 149,060 74,179 March 2016  37,441 March 2017  37,440 March 2018   2014 LTIP Award:  Three-year performance period award 204,741 204,741 68,249 March 2017  68,247 March 2018  68,245 March 2019  2015 LTIP Award:  Three-year performance period award 236,434 236,434 78,813 March 2018  78,812 March 2019  78,809 March 2020   2016 LTIP Award:  Three-year performance period award 324,469 * *   2017 LTIP Award:  Three-year performance period award 182,274 * *   Two-year performance period transition award 16,779 * *   One-year performance period transition award 28,379 25,541 8,514 March 2018  8,514 March 2019  8,513 March 2020 * Not yet earned as performance period not complete.  Note 6. Equity ‑Based Incentive Plans (Continued) 2013 Executive Incentive Compensation Plan (Executive Plan)  Pursuant to the company’s existing Executive Plan, certain senior management members of the company are eligible to receive cash bonuses based on predetermined formulas. In the event the bonus exceeds the predetermined maximum cash payout, the excess bonus up to a fixed percentage of base salary is distributed in shares of the company’s stock, of which one-third of the shares vest immediately and the remaining shares vest in equal annual installments over an additional two -year service-based vesting period requirement. The company’s stockholders approved the Executive Plan in May 2013, and 2.5 million shares of company stock were reserved for issuance through February 28, 2018. At December 31, 2017 , 2.1 million shares under the Executive Plan remained available for issuance. Pursuant to the Executive Plan, 117,000 shares were awarded with a market value of $5.3 million for the 2017 award year, 117,000 shares were awarded with a market value of $4.0 million for the 2016 award year , and no shares were awarded for the 2015 award year .  2014 Employee Stock Purchase Plan The 2014 Employee Stock Purchase Plan allows eligible employees, at their election, to purchase shares of the company’s stock at fair market value each month with a designated broker through payroll deductions. The maximum allowable payroll deduction for the plan, excluding company matching contributions, is $10,400 in any calendar year. The company provides matching contributions of 10% of employees’ payroll deductions. The company’s total expense for the plan was $558,000 , $514,000 , and $468,000 for the years ended December 31, 2017 , 2016 , and 2015 , respectively.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Financial Instruments
Derivative Financial Instruments	Note 7. Derivative Financial Instruments  The company is exposed to certain risks relating to its ongoing business operations. The company utilizes derivative instruments to mitigate commodity margin risk, occasionally to mitigate foreign currency exchange rate risk, and have in the past to mitigate interest rate fluctuation risk. The company routinely enters into forward exchange traded futures and option contracts to manage the price risk associated with nonferrous metals inventory, as well as purchases and sales of nonferrous metals (primarily aluminum and copper). The company offsets fair value amounts recognized for derivative instruments executed with the same counterparty under master netting agreements.  Commodity Futures Contracts . If the company is “long” on futures contracts, it means the company has more futures contracts purchased than futures contracts sold for the underlying commodity. If the company is “short” on a futures contract, it means the company has more futures contracts sold than futures contracts purchased for the underlying commodity . The following summarizes the company’s futures contract commitments as of December 31, 2017 (MT represents metric tons):     Commodity Futures Long/Short Total  Aluminum Long 1,550 MT  Aluminum Short 1,775 MT  Copper Long 5,555 MT  Copper Short 26,091 MT  The following summarizes the location and amounts of the fair values reported on the company’s balance sheets and gains or losses related to derivatives included in the company’s consolidated statements of operations as of and for the years ended December 31 (in thousands):      Asset Derivatives Liability Derivatives  Balance sheet Fair Value Fair Value  location December 31, 2017 December 31, 2016 December 31, 2017 December 31, 2016  Derivative instruments designated  as fair value hedges -  Commodity futures Other current assets $ 1,211 $ 2,910 $ 5,364 $ 1,300   Derivative instruments not designated  as hedges -  Commodity futures Other current assets 1,579 1,150 5,142 783  Total derivative instruments $ 2,790 $ 4,060 $ 10,506 $ 2,083   The fair value of the above derivative instruments along with required margin deposit amounts with the same counterparty under master netting agreements totaled $5.6 million and $3.2 million at December 31, 2017 , and 2016 , respectively, and are reflected in other current assets in the consolidated balance sheets.  Note 7. Derivative Financial Instruments (Continued)         Amount of  Location of gain gain (loss) Location of gain Amount of gain  (loss) recognized recognized in Hedged items in (loss) recognized (loss) recognized in  in income on income on fair value hedge in income on income on related  derivatives derivatives relationships related hedged items hedged items  For the Year Ended  December 31, 2017   Derivatives in fair value  hedging relationships -  Commodity futures Costs of goods sold $ 5,763 Firm commitments Costs of goods sold $ 1,814  Inventory Costs of goods sold 3,008  Derivatives not designated $ 4,822  as hedging instruments -  Commodity futures Costs of goods sold $ (18,784)      For the Year Ended  December 31, 2016   Derivatives in fair value  hedging relationships -  Commodity futures Costs of goods sold $ 3,596 Firm commitments Costs of goods sold $ (3,901)  Inventory Costs of goods sold (538)  Derivatives not designated $ (4,439)  as hedging instruments -  Commodity futures Costs of goods sold $ (8,450)      For the Year Ended  December 31, 2015   Derivatives in fair value  hedging relationships -  Commodity futures Costs of goods sold $ (4,254) Firm commitments Costs of goods sold $ 2,084  Inventory Costs of goods sold 1,269  Derivatives not designated $ 3,353  as hedging instruments -  Commodity futures Costs of goods sold $ 16,261   Derivatives accounted for as fair value hedges had ineffectiveness resulting in losses of $3,000 and $191,000 , and gains of $90,000 for the years ended December 31, 2017 , 2016, and 2015, respectively. Losses excluded from hedge effectiveness testing of $938,000 , $652,000 , and $991,000 increased cost of goods sold for the years ended December 31, 2017 , 2016, and 2015 , respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Measurements
Fair Value Measurements	Note 8. Fair Value Measurements Accounting standards provide a comprehensive framework for measuring fair value and sets forth a definition of fair value and establishes a hierarchy prioritizing the inputs to valuation techniques, giving the highest priority to quoted prices in active markets for identical assets and liabilities and the lowest priority to unobservable value inputs. Levels within the hierarchy are defined as follows:  · Level 1—Unadjusted quoted prices for identical assets and liabilities in active markets; · Level 2—Quoted prices for similar assets and liabilities in active markets (other than those included in Level 1) which are observable for the asset or liability, either directly or indirectly; and · Level 3—Valuations derived from valuation techniques in which one or more significant inputs or significant value drivers are unobservable.  The following table sets forth financial assets and liabilities measured at fair value on a recurring basis in the consolidated balance sheet and the respective levels to which the fair value measurements are classified within the fair value hierarchy as of December 31 (in thousands):      Quoted Prices Significant  in Active Other Significant  Markets for Observable Unobservable  Identical Assets Inputs Inputs  Total (Level 1) (Level 2) (Level 3)  December 31, 2017  Commodity futures – financial assets $ 2,790 $ - $ 2,790 $ -  Commodity futures – financial liabilities 10,506 - 10,506 -   December 31, 2016  Commodity futures – financial assets $ 4,060 $ - $ 4,060 $ -  Commodity futures – financial liabilities 2,083 - 2,083 -  The carrying amounts of financial instruments including cash and equivalents approximate fair value. The fair values of commodity futures contracts are estimated by the use of quoted market prices, estimates obtained from brokers, and other appropriate valuation techniques based on references available. The fair value of long-term debt, including current maturities, as determined by quoted market prices (Level 2), was approximately $2.5 billion for December 31, 2017 and 2016 (with a corresponding carrying amount in the consolidated balance sheet of $2.4 billion at December 31, 2017 and 2016 ). 

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies
Commitments and Contingencies	Note 9. Commitments and Contingencies The company has entered into certain commitments with suppliers which are of a customary nature. Commitments have been entered into relating to future expected requirements for such commodities as electricity, natural gas and its transportation services, fuel, air products, zinc and electrodes. Certain commitments contain provisions which require that the company “take or pay” for specified quantities at fixed prices without regard to actual usage for periods of up to 5 years for physical commodity requirements and commodity transportation requirements, and for up to 11 years for air products. The company utilized such “take or pay” requirements during the past three years under these contracts, except for certain air products at our Minnesota ironmaking operations which have been idle since May 2015. The company believes that production requirements will be such that consumption of the products or services purchased under these commitments will occur in the normal production process, other than certain air products related to Minnesota ironmaking operations during the idle period. The company’s commitments for these agreements with “take or pay” or other similar commitment provisions for the years ending December 31 are as follows (in thousands):    2018 $ 312,736  2019 116,779  2020 104,300  2021 90,894  2022 83,696  Thereafter 75,337  $ 783,742    Note 9. Commitments and Contingencies (Continued) At December 31, 2017 , the company has outstanding commitments of $74.7 million related to ongoing construction of property, plant, and equipment related primarily to steel operations. The company’s commitments for operating leases are discussed in Note 12. The company is involved in various routine litigation matters, including administrative proceedings, regulatory proceedings, governmental investigations, environmental matters, and commercial and construction contract disputes, none of which are expected to have a material impact on the company’s financial condition, results of operations, or liquidity. 

Transactions with Affiliated Co

Transactions with Affiliated Companies	12 Months Ended
	Dec. 31, 2017
Transactions with Affiliated Companies [Abstract]
Transactions with Affiliated Companies	Note 10. Transactions with Affiliated Companies The company sells flat roll products to and occasionally purchases ferrous materials from Heidtman. The president and chief executive officer of Heidtman was a member of the company’s board of directors through May 2017. Transactions with Heidtman for the years ended December 31, are as follows (in thousands):    2017 2016 2015  Sales $ 150,981 $ 142,624 $ 162,742  Percentage of consolidated net sales 2% 2% 2%  Accounts receivable 19,354 20,737 30,627  Purchases 10,684 9,017 11,429  Accounts payable 663 494 431  The company also purchases and sells recycled and scrap metal with other smaller affiliated companies. These transactions are as follows (in thousands):    2017 2016 2015  Sales $ 23,603 $ 27,305 $ 24,436  Accounts receivable 3,068 5,483 3,645  Purchases 219,975 165,091 178,102  Accounts payable 15,020 12,576 6,199   

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Retirement Plans	Note 11. Retirement Plans  The company sponsors several 401(k) retirement savings and profit sharing plans (Plans) for eligible employees, which are considered “qualified plans” for federal income tax purposes. The company’s total expense for the Plans was $92.5 million, $64.7 million, and $21.0 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. The company’s profit sharing component is 8% of consolidated pretax income excluding noncontrolling interests and other items. The resulting company profit sharing component was $80.7 million, $59.3 million, and $17.7 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively; of which $64.5 million, $47.5 million, and $14.1 million, respectively, was directed by the company’s board of directors to be contributed to the Plans, with the remaining amounts each year paid directly in cash to the Plans’ participants.

Leases

Leases	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Leases	Note 12. Leases The company has operating leases relating principally to transportation and other equipment and real estate. Certain leases include escalation clauses and/or purchase options. The company paid $18.9 million for operating leases for the years ended December 31, 2017 , and $15.1 million for the years ended December 31, 2016 and 2015 , respectively. At December 31, 2017 , future minimum payments for all non-cancelable operating leases with an initial or remaining term of one year or more are as follows (in thousands):     2018 $ 16,036  2019 12,609  2020 9,496  2021 5,868  2022 4,051  Thereafter 5,754  $ 53,814 

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Information
Segment Information	Note 13. Segment Information  The company’s operations are primarily organized and managed by reportable operating segments, which are steel operations, metals recycling operations, and steel fabrication operations. The segment operations are more fully described in Note 1 to the consolidated financial statements. Operating segment performance and resource allocations are primarily based on operating results before income taxes. The accounting policies of the reportable segments are consistent with those described in Note 1 to the consolidated financial statements. Intra ‑segment sales and any related profits are eliminated in consolidation. Amounts included in the category “Other” are from subsidiary operations that are below the quantitative thresholds required for reportable segments and primarily consist of our Minnesota ironmaking operations and several small joint ventures. In addition, “Other” also includes certain unallocated corporate accounts, such as the company’s senior secured credit facility, senior notes, certain other investments and certain profit sharing expenses. The company’s segment results are as follows (in thousands):     Metals Steel  For The Year Ended Steel Recycling Fabrication  December 31, 2017 Operations Operations Operations Other Eliminations Consolidated   Net Sales  External $ 6,613,944 $ 1,204,188 $ 823,630 $ 373,212 $ - $ 9,014,974  External Non-United States 317,819 205,853 151 - - 523,823  Other segments 243,646 1,402,963 644 2,299 (1,649,552) -  7,175,409 2,813,004 824,425 375,511 (1,649,552) 9,538,797  Operating income (loss) 1,098,630 71,052 87,295 (190,785) (1) 689 (2) 1,066,881  Income (loss) before income taxes 1,014,863 64,638 81,046 (226,001) 689 935,235  Depreciation and amortization 227,752 48,830 11,507 10,910 - 298,999  Capital expenditures 128,749 25,998 7,506 2,682 - 164,935   As of December 31, 2017   Assets $ 4,257,167 $ 1,011,298 $ 384,402 $ 1,334,361 (3) $ (131,496) (4) $ 6,855,732      Footnotes related to the year ended December 31, 2017, segment results (in millions):   (1) Corporate SG&A $ (49.4) (2) Gross profit increase from intra-company sales $ 0.7  Company-wide equity-based compensation (36.5)  Profit sharing (87.6)  Minnesota ironmaking operations (12.8)  Other, net (4.5)  $ (190.8)   (3) Cash and equivalents $ 1,003.2 (4) Elimination of intercompany receivables $ (106.1)  Accounts receivable 9.4 Elimination of intra-company debt (13.4)  Inventories 58.8 Other (12.0)  Income tax receivable 57.3 $ (131.5)  Property, plant and equipment, net 160.9  Intra-company debt 13.4  Other 31.4  $ 1,334.4         Note 13. Segment Information (Continued)     Metals Steel  For The Year Ended Steel Recycling Fabrication  December 31, 2016 Operations Operations Operations Other Eliminations Consolidated   Net Sales  External $ 5,399,275 $ 1,007,781 $ 700,852 $ 271,828 $ - $ 7,379,736  External Non-United States 235,436 161,560 189 188 - 397,373  Other segments 236,213 1,002,536 2,481 4,896 (1,246,126) -  5,870,924 2,171,877 703,522 276,912 (1,246,126) 7,777,109  Operating income (loss) 926,954 20,423 (5) 90,955 (301,116) (1) (9,250) (2) 727,966  Income (loss) before income taxes 836,818 8,378 (5) 82,776 (354,589) (9,250) 564,133  Depreciation and amortization 213,227 56,483 10,952 15,652 (205) 296,109  Capital expenditures 160,767 29,443 3,123 4,827 - 198,160   As of December 31, 2016   Assets $ 4,126,448 $ 1,038,946 $ 340,902 $ 1,054,448 (3) $ (137,012) (4) $ 6,423,732      Footnotes related to the year ended December 31, 2016, segment results (in millions):   (1) Corporate SG&A $ (48.9) (2) Gross profit decrease from intra-company sales $ (11.1)  Company-wide equity-based compensation (30.4) Non-cash asset impairment charges 1.8  Profit sharing (66.4) $ (9.3)  Minnesota ironmaking operations (15.8)  Minnesota ironmaking operations non-cash  asset impairment charges ($127.3 net  of eliminating amounts) (129.1)  Other, net (10.5)  $ (301.1)   (3) Cash and equivalents $ 775.7 (4) Elimination of intercompany receivables $ (112.3)  Accounts receivable 2.0 Elimination of intra-company debt (12.1)  Inventories 35.4 Other (12.6)  Income tax receivable 25.3 $ (137.0)  Property, plant and equipment, net 168.5  Intra-company debt 12.1  Other 35.4  $ 1,054.4   (5) Includes $5.5 million of non-cash goodwill  impairment charges.  Note 13. Segment Information (Continued)    Metals Steel  For The Year Ended Steel Recycling Fabrication  December 31, 2015 Operations Operations Operations Other Eliminations Consolidated   Net Sales  External $ 4,935,549 $ 1,249,061 $ 671,323 $ 283,965 $ - $ 7,139,898  External Non-United States 267,963 183,942 2,051 557 - 454,513  Other segments 218,963 904,713 25 30,325 (1,154,026) -  5,422,475 2,337,716 673,399 314,847 (1,154,026) 7,594,411  Operating income (loss) 403,216 (448,137) (3) 115,947 (148,784) (1) 4,974 (2) (72,784)  Income (loss) before income taxes 312,402 (465,426) (3) 108,795 (202,862) 4,974 (242,117)  Depreciation and amortization 205,827 65,640 9,587 13,746 (205) 294,595  Capital expenditures 71,752 21,874 3,395 17,480 - 114,501      Footnotes related to the year ended December 31, 2015, segment results (in millions):   (1) Corporate SG&A $ (37.8) (2) Gross profit increase from intra-company sales $ 5.0  Company-wide equity-based compensation (27.1)  Profit sharing (17.7)  Minnesota ironmaking operations (55.7)  Other, net (10.5)  $ (148.8)   (3) Includes $428.5 million of pretax non-cash asset  impairment charges.  

Condensed Consolidating Informa

Condensed Consolidating Information	12 Months Ended
	Dec. 31, 2017
Condensed Consolidating Information
Condensed Consolidating Information	 Note 14. Condensed Consolidating Information  Certain 100% owned subsidiaries of SDI have fully and unconditionally guaranteed jointly and severally all the indebtedness relating to the issuance of the company’s senior unsecured notes due 2021, 2023, 2024, 2025 and 2026. Following are the company’s condensed consolidating financial statements, including the guarantors, which present the financial position, results of operations, and cash flows of (i) SDI (in each case, reflecting investments in its consolidated subsidiaries under the equity method of accounting), (ii) the guarantor subsidiaries of SDI, (iii) the non-guarantor subsidiaries of SDI, and (iv) the eliminations necessary to arrive at the information on a consolidated basis. The following statements should be read in conjunction with the accompanying consolidated financial statements, and notes thereto.      Condensed Consolidating Balance Sheets (in thousands)  Combined Consolidating Total  As of December 31, 2017 Parent Guarantors Non-Guarantors Adjustments Consolidated  Cash and equivalents $ 1,001,405 $ 20,441 $ 6,803 $ - $ 1,028,649  Accounts receivable, net 274,968 1,426,036 37,387 (869,554) 868,837  Inventories 685,103 752,151 91,890 (9,797) 1,519,347  Other current assets 73,748 16,005 5,962 (4,206) 91,509  Total current assets 2,035,224 2,214,633 142,042 (883,557) 3,508,342  Property, plant and equipment, net 859,419 1,618,438 198,047 - 2,675,904  Intangible assets, net - 225,503 31,406 - 256,909  Goodwill - 379,069 7,824 - 386,893  Other assets, including investments in subs 2,512,594 6,622 5,505 (2,497,037) 27,684  Total assets $ 5,407,237 $ 4,444,265 $ 384,824 $ (3,380,594) $ 6,855,732   Accounts payable $ 168,282 $ 316,676 $ 101,948 $ (97,458) $ 489,448  Accrued expenses 222,023 254,196 10,243 (136,186) 350,276  Current maturities of long-term debt 731 - 56,454 (28,390) 28,795  Total current liabilities 391,036 570,872 168,645 (262,034) 868,519  Long-term debt 2,326,466 - 169,799 (143,120) 2,353,145  Other liabilities (661,839) 869,196 24,868 95,535 327,760  Total liabilities 2,055,663 1,440,068 363,312 (309,619) 3,549,424   Redeemable noncontrolling interests - - 111,240 - 111,240   Common stock 644 1,727,859 14,908 (1,742,767) 644  Treasury stock (665,297) - - - (665,297)  Additional paid-in capital 1,141,534 128,076 797,196 (925,272) 1,141,534  Retained earnings (deficit) 2,874,693 1,148,262 (745,326) (402,936) 2,874,693  Total Steel Dynamics, Inc. equity 3,351,574 3,004,197 66,778 (3,070,975) 3,351,574  Noncontrolling interests - - (156,506) - (156,506)  Total equity 3,351,574 3,004,197 (89,728) (3,070,975) 3,195,068  Total liabilities and equity $ 5,407,237 $ 4,444,265 $ 384,824 $ (3,380,594) $ 6,855,732  Note 14. Condensed Consolidating Information (Continued)      Combined Consolidating Total  As of December 31, 2016 Parent Guarantors Non-Guarantors Adjustments Consolidated  Cash and equivalents $ 766,685 $ 54,677 $ 20,121 $ - $ 841,483  Accounts receivable, net 229,148 1,257,245 23,689 (780,298) 729,784  Inventories 587,319 639,148 58,696 (9,952) 1,275,211  Other current assets 45,049 36,062 4,447 (2,361) 83,197  Total current assets 1,628,201 1,987,132 106,953 (792,611) 2,929,675  Property, plant and equipment, net 899,370 1,679,751 208,094 - 2,787,215  Intangible assets, net - 251,919 32,058 - 283,977  Goodwill - 385,527 7,824 - 393,351  Other assets, including investments in subs 2,769,884 7,335 5,832 (2,753,537) 29,514  Total assets $ 5,297,455 $ 4,311,664 $ 360,761 $ (3,546,148) $ 6,423,732   Accounts payable $ 141,089 $ 265,764 $ 89,659 $ (101,316) $ 395,196  Accrued expenses 198,085 220,917 8,793 (113,808) 313,987  Current maturities of long-term debt 674 700 29,347 (27,089) 3,632  Total current liabilities 339,848 487,381 127,799 (242,213) 712,815  Long-term debt 2,324,298 - 168,566 (139,670) 2,353,194  Other liabilities (293,711) 1,219,444 42,482 (499,191) 469,024  Total liabilities 2,370,435 1,706,825 338,847 (881,074) 3,535,033   Redeemable noncontrolling interests - - 111,240 - 111,240   Common stock 641 1,727,859 14,908 (1,742,767) 641  Treasury stock (416,829) - - - (416,829)  Additional paid-in capital 1,132,749 128,076 779,678 (907,754) 1,132,749  Retained earnings (deficit) 2,210,459 748,904 (734,351) (14,553) 2,210,459  Total Steel Dynamics, Inc. equity 2,927,020 2,604,839 60,235 (2,665,074) 2,927,020  Noncontrolling interests - - (149,561) - (149,561)  Total equity 2,927,020 2,604,839 (89,326) (2,665,074) 2,777,459  Total liabilities and equity $ 5,297,455 $ 4,311,664 $ 360,761 $ (3,546,148) $ 6,423,732 Note 14. Condensed Consolidating Information (Continued)      Condensed Consolidating Statements of Operations (in thousands)   Combined Consolidating Total  For the year ended December 31, 2017 Parent Guarantors Non-Guarantors Adjustments Consolidated  Net sales $ 3,702,597 $ 10,366,526 $ 597,789 $ (5,128,115) $ 9,538,797  Costs of goods sold 2,994,257 9,399,996 577,205 (5,014,675) 7,956,783  Gross profit 708,340 966,530 20,584 (113,440) 1,582,014  Selling, general and administrative 221,736 293,161 20,493 (20,257) 515,133  Operating income (loss) 486,604 673,369 91 (93,183) 1,066,881  Interest expense, net of capitalized interest 73,521 57,622 12,901 (9,645) 134,399  Other (income) expense, net (2,305) (9,937) (156) 9,645 (2,753)  Income (loss) before income taxes and  equity in net income of subsidiaries 415,388 625,684 (12,654) (93,183) 935,235  Income taxes (benefit) (69,961) 226,327 5,266 (32,193) 129,439  485,349 399,357 (17,920) (60,990) 805,796  Equity in net income of subsidiaries 327,392 - - (327,392) -  Net loss attributable to noncontrolling interests - - 6,945 - 6,945  Net income (loss) attributable to Steel Dynamics, Inc. $ 812,741 $ 399,357 $ (10,975) $ (388,382) $ 812,741      Combined Consolidating Total  For the year ended December 31, 2016 Parent Guarantors Non-Guarantors Adjustments Consolidated  Net sales $ 3,037,801 $ 8,356,727 $ 388,071 $ (4,005,490) $ 7,777,109  Costs of goods sold 2,428,863 7,522,791 390,313 (3,899,722) 6,442,245  Gross profit (loss) 608,938 833,936 (2,242) (105,768) 1,334,864  Selling, general and administrative 196,442 281,071 16,103 (19,557) 474,059  Asset impairment charges 12,700 5,500 116,445 (1,806) 132,839  Operating income (loss) 399,796 547,365 (134,790) (84,405) 727,966  Interest expense, net of capitalized interest 71,182 72,420 10,874 (8,439) 146,037  Other (income) expense, net 14,200 (5,363) 520 8,439 17,796  Income (loss) before income taxes and  equity in net loss of subsidiaries 314,414 480,308 (146,184) (84,405) 564,133  Income taxes (benefit) 69,454 180,990 (15,825) (30,492) 204,127  244,960 299,318 (130,359) (53,913) 360,006  Equity in net loss of subsidiaries 137,155 - - (137,155) -  Net loss attributable to noncontrolling interests - - 22,109 - 22,109  Net income (loss) attributable to Steel Dynamics, Inc. $ 382,115 $ 299,318 $ (108,250) $ (191,068) $ 382,115   Note 14. Condensed Consolidating Information (Continued)     Combined Consolidating Total  For the year ended December 31, 2015 Parent Guarantors Non-Guarantors Adjustments Consolidated  Net sales $ 2,908,904 $ 8,132,043 $ 361,944 $ (3,808,480) $ 7,594,411  Costs of goods sold 2,515,621 7,646,411 420,281 (3,719,620) 6,862,693  Gross profit (loss) 393,283 485,632 (58,337) (88,860) 731,718  Selling, general and administrative 128,929 254,106 11,893 (18,926) 376,002  Asset impairment charges - 428,500 - - 428,500  Operating income (loss) 264,354 (196,974) (70,230) (69,934) (72,784)  Interest expense, net of capitalized interest 75,457 76,009 6,969 (4,485) 153,950  Other (income) expense, net 13,970 332 (3,404) 4,485 15,383  Income (loss) before income taxes and  equity in net loss of subsidiaries 174,927 (273,315) (73,795) (69,934) (242,117)  Income taxes (benefit) (124,626) 61,571 (4,627) (29,265) (96,947)  299,553 (334,886) (69,168) (40,669) (145,170)  Equity in net loss of subsidiaries (429,864) - - 429,864 -  Net loss attributable to noncontrolling interests - - 14,859 - 14,859  Net income (loss) attributable to Steel Dynamics, Inc. $ (130,311) $ (334,886) $ (54,309) $ 389,195 $ (130,311)      Condensed Consolidating Statements of Cash Flows (in thousands)   Combined Consolidating Total  For the year ended December 31, 2017 Parent Guarantors Non-Guarantors Adjustments Consolidated   Net cash provided by (used in) operating activities $ 171,300 $ 594,279 $ (31,719) $ 5,746 $ 739,606  Net cash used in investing activities (62,534) (73,021) (8,301) 4,751 (139,105)  Net cash provided by (used in) financing activities 125,954 (555,494) 26,702 (10,497) (413,335)  Increase (decrease) in cash and equivalents 234,720 (34,236) (13,318) - 187,166  Cash and equivalents at beginning of period 766,685 54,677 20,121 - 841,483  Cash and equivalents at end of period $ 1,001,405 $ 20,441 $ 6,803 $ - $ 1,028,649       Combined Consolidating Total  For the year ended December 31, 2016 Parent Guarantors Non-Guarantors Adjustments Consolidated   Net cash provided by operating activities $ 326,216 $ 517,699 $ 6,057 $ 2,797 $ 852,769  Net cash used in investing activities (161,043) (140,027) (9,578) (2,245) (312,893)  Net cash provided by (used in) financing activities (35,365) (404,971) 15,463 (552) (425,425)  Increase (decrease) in cash and equivalents 129,808 (27,299) 11,942 - 114,451  Cash and equivalents at beginning of period 636,877 81,976 8,179 - 727,032  Cash and equivalents at end of period $ 766,685 $ 54,677 $ 20,121 $ - $ 841,483  Note 14. Condensed Consolidating Information (Continued)     Combined Consolidating Total  For the year ended December 31, 2015 Parent Guarantors Non-Guarantors Adjustments Consolidated   Net cash provided by operating activities $ 436,012 $ 594,437 $ 19,388 $ 3,788 $ 1,053,625  Net cash used in investing activities (64,457) (82,751) (15,703) 20,284 (142,627)  Net cash provided by (used in) financing activities 9 (511,400) (9,866) (24,072) (545,329)  Increase (decrease) in cash and equivalents 371,564 286 (6,181) - 365,669  Cash and equivalents at beginning of period 265,313 81,690 14,360 - 361,363  Cash and equivalents at end of period $ 636,877 $ 81,976 $ 8,179 $ - $ 727,032 

Quarterly Financial Information

Quarterly Financial Information	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information
Quarterly Financial Information	 Note 15. Quarterly Financial Information (unaudited, in thousands, except per share data)    1 st Quarter 2 nd Quarter 3 rd Quarter 4 th Quarter  2017:  Net Sales $ 2,368,216 $ 2,390,720 $ 2,443,382 $ 2,336,479  Gross profit 472,154 392,518 396,518 320,824  Operating income 334,566 265,353 271,015 195,947  Net income 198,666 152,947 151,012 303,171  Net income attributable to Steel Dynamics, Inc. 200,817 153,933 153,258 304,733  Earnings per share:  Basic 0.83 0.64 0.64 1.28  Diluted 0.82 0.63 0.64 1.28   2016:  Net Sales $ 1,741,301 $ 2,023,902 $ 2,101,310 $ 1,910,596  Gross profit 236,036 380,383 408,503 309,942  Operating income 131,965 256,122 283,855 56,024  Net income 61,318 140,443 154,413 3,832  Net income attributable to Steel Dynamics, Inc. 62,737 141,969 157,397 20,012  Earnings per share:  Basic 0.26 0.58 0.65 0.08  Diluted 0.26 0.58 0.64 0.08   The fourth quarter of 2017 net income and net income attributable to Steel Dynamics, Inc. reflects $180.6 million of tax benefit related primarily to the impacts of the revaluation of the company’s deferred tax liabilities as of December 31, 2017, using the lower federal tax rate enacted in the Tax Cuts and Jobs Act of 2017.  The fourth quarter of 2016 reflects non-cash asset impairment charges associated with the company’s Minnesota ironmaking operations and certain OmniSource goodwill, which reduced operating and pretax income by $132.8 million, net income by $89.5 million and net income attributable to Steel Dynamics, Inc. by $76.4 million. The fourth quarter of 2016 also reflects non-operating expenses of $16.5 million associated with call premiums and the write off of deferred financing costs related to the refinancing of $400.0 million of outstanding 6.125% Senior Notes due 2019 with $400.0 million 5.000% Senior Notes due 2026, and repayment of the $228.1 million outstanding senior secured term debt.  Earnings per share are computed independently for each of the quarters presented. Therefore, the sum of the quarterly earnings per share may not equal the total for the year.

Description of the Business a22

Description of the Business and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Description of the Business and Significant Accounting Policies
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of SDI, together with its wholly- and majority-owned or controlled subsidiaries, after elimination of intercompany accounts and transactions. Noncontrolling interests represent the noncontrolling owner’s proportionate share in the equity, income, or losses of the company’s majority-owned or controlled consolidated subsidiaries.
Use of Estimates	Use of Estimates These consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States, and accordingly, include amounts that require management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and in the notes thereto. Significant items subject to such estimates and assumptions include the carrying value of property, plant and equipment, intangible assets, and goodwill; valuation allowances for trade receivables, inventories and deferred income tax assets; unrecognized tax benefits; potential environmental liabilities; and litigation claims and settlements. Actual results may differ from these estimates and assumptions.
Goodwill	Note 1. Description of the Business and Summary of Significant Accounting Policies (Continued) Goodwill The company’s goodwill is allocated to the following reporting units at December 31 (in thousands):   2017 2016  Steel Operations Segment  Columbus Flat Roll Division $ 19,682 $ 19,682  The Techs 142,783 142,783  Vulcan Threaded Products 7,824 7,824  Roanoke Bar Division 29,041 29,041  Metals Recycling Operations Segment  OmniSource 90,638 97,096  Indiana Steel Mills 95,000 95,000  Steel Fabrication Operations Segment – New Millennium Building Systems 1,925 1,925  $ 386,893 $ 393,351  OmniSource goodwill decreased $6.5 million in 2017 in recognition of the 2017 tax benefit related to the normal amortization of the component of OmniSource tax-deductible goodwill in excess of book goodwill. In 2016, a $5.5 million OmniSource goodwill impairment charge was recorded in conjunction with OmniSource entering into a definitive sale agreement with a third-party pertaining to certain OmniSource long-lived assets (classified and reported as held for sale as of December 31, 2016), inventory and spare parts, as provided under ASC 350. In 2015, a $341.3 million OmniSource goodwill impairment charge was recorded pursuant to the company’s annual review for impairment of goodwill and indefinite-lived intangible assets, as discussed further under “Impairment of Goodwill and Indefinite-Lived Intangible Assets” below. Cumulative OmniSource goodwill impairment charges were $346.8 million at December 31, 2017 and 2016.
Recently Issued Accounting Standards	Recently Adopted/Issued Accounting Standards  In May 2014, the FASB issued ASU 2014-09, which is codified in ASC 606, Revenue Recognition – Revenue from Contracts with Customers, which amends the guidance in former ASC 605, Revenue Recognition . FASB has since issued clarifying guidance in the form of ASU 2016-08, Revenue from Contracts with Customers: Principal versus Agent Consideration (Reporting Revenue Gross versus Net) , ASU 2016-10, Revenue from Contract with Customers: Identifying Performance Obligations and Licensing , and ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients, collectively (ASC 606). The core principle of ASC 606 is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASC 606 also requires additional disclosures to help users of financial statements better understand the nature, amount, timing, and potential uncertainty of revenue that is recognized. ASC 606 guidance is effective for annual and interim periods beginning after December 15, 2017, but could have been early adopted for annual and interim periods ending after December 15, 2016, using a full retrospective or modified retrospective approach. The company has completed its adoption plan in which it identified revenue streams, and analyzed those revenue streams, based on a detailed review of its business and contracts, pursuant to the new accounting requirements. The company concluded that there will be no change in the amount or timing of revenue recognized under the new standard, or significant changes required to the company’s functions, processes or systems. The company has adopted ASC 606 in the first quarter of 2018 using the modified retrospective approach. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842): which establishes a new lease accounting model that requires lessees to recognize a right of use asset and related lease liability for most leases having lease terms of more than 12 months (ASU 2016-02). Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. This new guidance is effective for annual and interim periods beginning after December 15, 2018, but can be early adopted. The company is currently evaluating the impact of the provisions of ASU 2016-02, and anticipates adopting on January 1, 2019.
Revenue Recognition and Allowances for Doubtful Accounts	Revenue Recognition and Allowances for Doubtful Accounts  Except for the steel fabrication operations, the company recognizes revenues from sales and the allowance for estimated returns and claims from these sales at the time the title of the product transfers, upon shipment. Provision is made for estimated product returns and customer claims based on historical experience. If the historical data used in the estimates does not reflect future returns and claims trends, additional provision may be necessary. The company’s steel fabrication operations recognize revenues utilizing a percentage of completion methodology based on steel tons used on completed units to date as a percentage of estimated total steel tons required for each contract. The allowance for doubtful accounts for all operating segments is based on the company’s best estimate of probable credit losses, along with historical experience. 
Cash and Equivalents	Cash and Equivalents Cash and equivalents include all highly liquid investments with a maturity of three months or less at the date of acquisition. Restricted cash is primarily funds held in escrow as required by various insurance and government organizations.
Inventories	Inventories Inventories are stated at lower of cost or net realizable value. Cost is determined using a weighted average cost method for raw materials and supplies, and on a first-in, first-out basis for other inventory . Inventory consisted of the following at December 31 (in thousands):     2017 2016  Raw materials $ 675,715 $ 515,924  Supplies 374,515 383,134  Work in progress 128,565 103,606  Finished goods 340,552 272,547  Total inventories $ 1,519,347 $ 1,275,211 
Property, Plant and Equipment	  2017 2016  Raw materials $ 675,715 $ 515,924  Supplies 374,515 383,134  Work in progress 128,565 103,606  Finished goods 340,552 272,547  Total inventories $ 1,519,347 $ 1,275,211  Property, Plant and Equipment Property, plant and equipment are stated at cost, which includes capitalized interest on construction in progress amounts, and is reduced by proceeds received from certain state and local government grants and other capital cost reimbursements. The company assigns each fixed asset a useful life ranging from 3 to 20 years for plant, machinery and equipment, and 10 to 40 years for buildings and improvements. Repairs and maintenance are expensed as incurred. Depreciation is provided utilizing the straight-line depreciation methodology, or the units-of-production depreciation methodology for certain production related assets, based on units produced, subject to a minimum and maximum level. Depreciation expense was $263.7 million, $260.6 million, and $263.2 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. Refer to Impairment of Long-Lived Tangible and Definite-Lived Intangible Assets below in Note 1 for discussions regarding the impairments of various property, plant and equipment in 2016 and 2015 .  The company’s property, plant and equipment consisted of the following at December 31 (in thousands):      2017 2016  Land and improvements $ 314,854 $ 311,005  Buildings and improvements 723,504 709,809  Plant, machinery and equipment 4,035,717 3,975,560  Construction in progress 91,433 70,615  5,165,508 5,066,989  Less accumulated depreciation 2,489,604 2,279,774  Property, plant and equipment, net $ 2,675,904 $ 2,787,215 
Intangible Assets	Intangible Assets The company’s intangible assets consisted of the following at December 31 (in thousands):    Weighted  Average  Useful Amortization  2017 2016 Life Period  Customer and scrap generator relationships $ 394,062 $ 446,688 5 to 25 years 21 years  Trade names 130,550 130,550 15 to 25 years 18 years  Other 2,165 1,415 3 to 5 years 4 years  526,777 578,653 20 years  Less accumulated amortization 269,868 294,676  $ 256,909 $ 283,977  The company utilizes an accelerated amortization methodology for customer and scrap generator relationships in order to follow the pattern in which the economic benefits of the amounts are anticipated to be consumed. Trade names are amortized using a straight-line methodology. Amortization of intangible assets was $29.2 million, $28.8 million, and $24.2 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively . Estimated amortization expense related to amortizable intangibles for the years ending December 31 is as follows (in thousands):     2018 $ 26,910  2019 24,823  2020 22,629  2021 20,840  2022 19,231  Thereafter 142,476  Total $ 256,909 
Impairment of Long-Lived Tangible and Definite-Lived Intangible Assets	   2018 $ 26,910  2019 24,823  2020 22,629  2021 20,840  2022 19,231  Thereafter 142,476  Total $ 256,909  Impairment of Long-Lived Tangible and Definite ‑Lived Intangible Assets The company reviews long-lived assets for impairment whenever events or changes in circumstances indicate the carrying amount of such assets may not be fully recoverable. Impairment losses are recorded on long-lived assets used in operations when indicators of impairment are present and the undiscounted cash flows estimated to be generated by those assets are less than the assets’ carrying amounts. The impairment loss is measured by comparing the fair value of the assets to its carrying amount. The company considers various factors and determines whether an impairment test is necessary, including by way of examples, a significant and prolonged deterioration in operating results and/or projected cash flows, significant changes in the extent or manner in which an asset is used, technological advances with respect to assets which would potentially render them obsolete, our strategy and capital planning, and the economic climate in markets to be served.  A long-lived asset is classified as held for sale upon meeting specified criteria related to ability and intent to sell. An asset classified as held for sale is measured at the lower of its carrying amount or fair value less cost to sell. As of December 31, 2017 and 2016, the company reported $8.7 and $29.3 million, respectively, of assets held for sale within other current assets in our consolidated balance sheet. An impairment loss is recognized for any initial or subsequent write-down of the asset held for sale to its fair value less cost to sell. For assets determined to be classified as held for sale in the year ended December 31, 2017 and 2016, the asset carrying amounts approximated their fair value less cost to sell. The company recorded a $10.3 million asset impairment charge in the consolidated statement of operations for assets determined to be classified as held for sale in the year ended December 31, 2015. The company determined fair value using Level 3 fair value inputs as provided for under ASC 820, consisting of information provided by brokers and other external sources along with management’s own assumptions.  Significant events occurred during the fourth quarter of 2016, including the previously noted termination of all existing agreements with the Mining Resources noncontrolling investor, that represented impairment indicators related primarily to Mining Resources and Mesabi Mining fixed assets within our Minnesota ironmaking operations. The company therefore undertook a fourth quarter 2016 assessment of the recoverability of the carrying amounts of primarily our Mining Resources and Mesabi Mining operation’s fixed assets. With the company’s outlook at the time of this 2016 assessment regarding future cash flows, the company concluded that the carrying amounts of the fixed assets were no longer fully recoverable, and they were in fact impaired. This 2016 assessment resulted in a non-cash asset impairment charge of $127.3 million, including amounts attributable to noncontrolling interests of $13.1 million, which reduced net income attributable to Steel Dynamics, Inc. by $72.9 million for the year ended December 31, 2016. The carrying values of the impaired assets were adjusted to their estimated fair values at that time as determined primarily on the cost approach, as well as expected future discounted cash flows (an income approach), using Level 3 fair value inputs as provided for under ASC 820. Note 1. Description of the Business and Summary of Significant Accounting Policies (Continued)
Impairment of Goodwill and Indefinite-Lived Intangible Assets	Impairment of Goodwill and Indefinite ‑Lived Intangible Assets At least once annually (as of October 1) or when indicators of impairment exist, the company performs an impairment test for goodwill. Goodwill is allocated to various reporting units, which are generally one level below the company’s operating segments. The company utilizes a two-stepped approach to evaluate goodwill impairment. The first step of the test determines if there is potential goodwill impairment. In this step, the company compares the fair value of the reporting unit to its carrying amount (which includes goodwill). The fair value of the reporting unit is determined by using an estimate of future cash flows utilizing a risk-adjusted discount rate to calculate the net present value of future cash flows (income approach), and by using a market approach based upon an analysis of valuation metrics of comparable peer companies, using Level 3 fair value inputs as provided for under ASC 820. If the fair value exceeds the carrying value, there is no impairment. If the carrying amount exceeds the fair value, the company performs the second step of the test, which measures the amount of impairment loss to be recorded. In the second step, the company compares the carrying amount of the goodwill to the implied fair value of the goodwill based on the net fair value of the recognized and unrecognized assets and liabilities of the reporting unit to which it is allocated. If the implied fair value is less than the carrying value, an impairment loss is recorded to the extent that the fair value of the goodwill is less than its carrying value. At least once annually (as of October 1) or when indicators of impairment exist, the company tests indefinite-lived intangible assets for impairment through the comparison of the fair value of the specific intangible asset with its carrying amount. The fair value of the intangible asset is determined by using an estimate of future cash flows attributable to the asset and a risk-adjusted discount rate to compute a net present value of future cash flows (income approach). If the fair value is less than the carrying value, an impairment loss is recorded in an amount equal to the excess in carrying value. During the company’s 2015 annual goodwill and indefinite-lived intangible asset impairment analysis, the company determined that the fair value of OmniSource was less than its carrying value, and upon the completion of the second step of the impairment analysis, that the goodwill and trade name indefinite-lived intangible assets were impaired. The OmniSource goodwill and trade name indefinite-lived intangible assets were written down to their respective fair values at that time, resulting in non-cash asset impairment charge of $341.3 million and $68.5 million, respectively, that are reflected in asset impairment charge in the consolidated statement of operations for the year ended December 31, 2015, within the metals recycling operations. No impairment was identified during the company’s 2017 and 2016 annual goodwill and indefinite-lived intangible asset impairment analysis.
Equity-Based Compensation	Equity ‑Based Compensation The company has several stock ‑based employee compensation plans which are more fully described in Note 6 Equity-Based Incentive Plans . Compensation expense for restricted stock units, deferred stock units, restricted stock, and performance awards is recorded over the vesting periods using the fair value as determined by the closing fair market value of the company’s common stock on the grant date, and with respect to performance awards, an estimate of probability of award achievement during the performance period. The company recognizes forfeitures as they Note 1. Description of the Business and Summary of Significant Accounting Policies (Continued) occur. Compensation expense for these stock ‑based employee compensation plans was $36.6 million, $30.4 million, and $27.1 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively.
Income Taxes	Income Taxes The company accounts for income taxes and the related accounts under the liability method. Deferred tax liabilities and assets are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted rates expected to be in effect during the year in which the basis differences reverse.
Earnings Per Share	Earnings Per Share Basic earnings per share is based on the weighted average shares of common stock outstanding during the period. Diluted earnings per share assumes the weighted average dilutive effect of common share equivalents outstanding during the period applied to the company’s basic earnings per share. Common share equivalents represent potentially dilutive restricted stock units, deferred stock units, restricted stock, and performance awards, and are excluded from the computation in periods in which they have an anti-dilutive effect. There were no anti-dilutive common stock equivalents as of and for the years ended December 31, 2017 and 2016 . There were 1.5 million anti-dilutive common stock equivalents as of and for the year ended December 31, 2015 . The following table presents a reconciliation of the numerators and the denominators of the company’s basic and diluted earnings per share computations for the years ended December 31 (in thousands, except per share data):      2017 2016  Net Income Shares Per Share Net Income Shares Per Share  (Numerator) (Denominator) Amount (Numerator) (Denominator) Amount  Basic earnings per share $ 812,741 240,132 $ 3.38 $ 382,115 243,576 $ 1.57  Dilutive common share equivalents - 1,649 - 1,722  Diluted earnings per share $ 812,741 241,781 $ 3.36 $ 382,115 245,298 $ 1.56     2015  Net Loss Shares Per Share  (Numerator) (Denominator) Amount  Basic earnings per share $ (130,311) 242,017 $ (0.54)  Dilutive common share equivalents - -  Diluted earnings per share $ (130,311) 242,017 $ (0.54)  
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the company to significant concentrations of credit risk principally consist of temporary cash investments and accounts receivable. The company places its temporary cash investments with high credit quality financial institutions and companies, and limits the amount of credit exposure from any one entity. The company is exposed to credit risk in the event of nonpayment by customers. The company mitigates its exposure to credit risk, which it generally extends initially on an unsecured basis, by performing ongoing credit evaluations and taking further action if necessary, such as requiring letters of credit or other security interests to support the customer receivable. Management’s estimation of the allowance for doubtful accounts is based upon known credit risks, historical loss experience and current economic conditions affecting the company’s customers. Customer accounts receivable are charged off when all collection efforts have been exhausted and the amounts are deemed uncollectible. Heidtman Steel Products (Heidtman), a related party, accounted for 2% and 3% of the company’s net accounts receivable at December 31, 2017 , and December 31, 2016 .
Derivative Financial Instruments	Derivative Financial Instruments The company recognizes all derivatives as either assets or liabilities in the consolidated balance sheets and measures those instruments at fair value. Derivatives that are not designated as hedges must be adjusted to fair value through earnings. Changes in the fair value of derivatives that are designated as hedges, depending on the nature of the hedge, are recognized as either an offset against the change in fair value of the hedged balance sheet item in the case of fair value hedges or as other comprehensive income in the case of cash flow hedges, until the hedged item is recognized in earnings. The ineffective portion of a derivative’s change in fair value is immediately recognized in earnings. The company offsets fair value amounts recognized for derivative instruments executed with the same counterparty under master netting agreements. Note 1. Description of the Business and Summary of Significant Accounting Policies (Continued) In the normal course of business, the company has derivative financial instruments in the form of forward contracts in various commodities, may have involvement with derivative financial instruments related to managing fluctuations in foreign exchange rates, and in the past has had derivative financial instruments related to managing fluctuations in interest rates. At the time of acquiring these financial instruments, the company designates and assigns these instruments as hedges of specific assets, liabilities or anticipated transactions. When hedged assets or liabilities are sold or extinguished, or the anticipated transaction being hedged is no longer expected to occur, the company recognizes the gain or loss on the designated hedged financial instrument. The company routinely enters into forward contracts in various commodities, primarily nonferrous metals (specifically aluminum and copper) in our metals recycling operations, to reduce exposure to commodity related price fluctuations. The company does not enter into these derivative financial instruments for speculative purposes.

Description of the Business a23

Description of the Business and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Description of the Business and Significant Accounting Policies
Schedule of Inventories	. Inventory consisted of the following at December 31 (in thousands):     2017 2016  Raw materials $ 675,715 $ 515,924  Supplies 374,515 383,134  Work in progress 128,565 103,606  Finished goods 340,552 272,547  Total inventories $ 1,519,347 $ 1,275,211 
Schedule of Property, Plant and Equipment	 The company’s property, plant and equipment consisted of the following at December 31 (in thousands):      2017 2016  Land and improvements $ 314,854 $ 311,005  Buildings and improvements 723,504 709,809  Plant, machinery and equipment 4,035,717 3,975,560  Construction in progress 91,433 70,615  5,165,508 5,066,989  Less accumulated depreciation 2,489,604 2,279,774  Property, plant and equipment, net $ 2,675,904 $ 2,787,215 
Schedule of Finite-Lived Intangible Assets	The company’s intangible assets consisted of the following at December 31 (in thousands):    Weighted  Average  Useful Amortization  2017 2016 Life Period  Customer and scrap generator relationships $ 394,062 $ 446,688 5 to 25 years 21 years  Trade names 130,550 130,550 15 to 25 years 18 years  Other 2,165 1,415 3 to 5 years 4 years  526,777 578,653 20 years  Less accumulated amortization 269,868 294,676  $ 256,909 $ 283,977 
Schedule of Intangible Assets, Future Amortization Expense	. Estimated amortization expense related to amortizable intangibles for the years ending December 31 is as follows (in thousands):     2018 $ 26,910  2019 24,823  2020 22,629  2021 20,840  2022 19,231  Thereafter 142,476  Total $ 256,909 
Schedule of Goodwill	The company’s goodwill is allocated to the following reporting units at December 31 (in thousands):   2017 2016  Steel Operations Segment  Columbus Flat Roll Division $ 19,682 $ 19,682  The Techs 142,783 142,783  Vulcan Threaded Products 7,824 7,824  Roanoke Bar Division 29,041 29,041  Metals Recycling Operations Segment  OmniSource 90,638 97,096  Indiana Steel Mills 95,000 95,000  Steel Fabrication Operations Segment – New Millennium Building Systems 1,925 1,925  $ 386,893 $ 393,351 
Reconciliation of Basic and Diluted Earnings Per Share	The following table presents a reconciliation of the numerators and the denominators of the company’s basic and diluted earnings per share computations for the years ended December 31 (in thousands, except per share data):      2017 2016  Net Income Shares Per Share Net Income Shares Per Share  (Numerator) (Denominator) Amount (Numerator) (Denominator) Amount  Basic earnings per share $ 812,741 240,132 $ 3.38 $ 382,115 243,576 $ 1.57  Dilutive common share equivalents - 1,649 - 1,722  Diluted earnings per share $ 812,741 241,781 $ 3.36 $ 382,115 245,298 $ 1.56     2015  Net Loss Shares Per Share  (Numerator) (Denominator) Amount  Basic earnings per share $ (130,311) 242,017 $ (0.54)  Dilutive common share equivalents - -  Diluted earnings per share $ (130,311) 242,017 $ (0.54)  

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Long-Term Debt
Schedule of Long-term Debt Instruments	The company’s borrowings consisted of the following at December 31 (in thousands):    2017 2016  5.125% senior notes due 2021 $ 700,000 $ 700,000  5 1 / 4 % senior notes due 2023 400,000 400,000  5.500% senior notes due 2024 500,000 500,000  4.125% senior notes due 2025 350,000 -  5.000% senior notes due 2026 400,000 400,000  6 3 / 8 % senior notes due 2022 - 350,000  Other obligations 58,852 36,791  Total debt 2,408,852 2,386,791  Less debt issuance costs 26,912 29,965  Total amounts outstanding 2,381,940 2,356,826  Less current maturities 28,795 3,632  Long-term debt $ 2,353,145 $ 2,353,194 
Schedule of Debt	      Issue 2021 Notes 2023 Notes 2024 Notes 2025 Notes 2026 Notes  Outstanding Balance $700.0 million $400.0 million $500.0 million $350.0 million $400.0 million  Stated Interest Rate 5.125% 5 1 / 4 % 5.500% 4.125% 5.000%  Semi-Annual Interest Payment Dates April 1 and April 15 and April 1 and March 15 and June 15 and  October 1 October 15 October 1 September 15 December 15  Equity Redemption Option Price & Date N/A – date N/A – date N/A – date 104.125% 105.000%  passed passed passed September 15, 2020 December 15, 2019  “Make-Whole” Option Date N/A – date passed April 15, 2018 October 1, 2019 September 15, 2020 December 15, 2021  First Call Price & Date N/A – date 102.625% 102.750% 102.063% 102.500%  passed April 15, 2018 October 1, 2019 September 15, 2020 December 15, 2021  Second Call Price & Date 101.281% 101.750% 101.833% 101.031% 101.667%  October 1, 2018 April 15, 2019 October 1, 2020 September 15, 2021 December 15, 2022  Third Call Price & Date 100.000% 100.875% 100.917% 100.000% 100.833%  October 1, 2019 April 15, 2020 October 1, 2021 September 15, 2022 December 15, 2023  Fourth Call Price & Date - 100.000% 100.000% - 100.000%  April 15, 2021 October 1, 2022 December 15, 2024  Maturity Date October 1, 2021 April 15, 2023 October 1, 2024 September 15, 2025 December 15, 2026  
Schedule of Maturities of Long-term Debt	Maturities of outstanding debt as of December 31, 2017 , are as follows (in thousands):    2018 $ 28,795  2019 3,291  2020 3,492  2021 703,708  2022 3,174  Thereafter 1,666,392  $ 2,408,852 

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Taxes
Schedule of Components of Income Tax Expense (Benefit)	   2017 2016 2015  Current income tax expense $ 269,387 $ 153,176 $ 6,391  Deferred income tax expense (benefit) (139,948) 50,951 (103,338)  Total income tax expense (benefit) $ 129,439 $ 204,127 $ (96,947)  A reconciliation of the statutory rates to the actual effective tax rates for the years ended December 31 are as follows:
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the statutory rates to the actual effective tax rates for the years ended December 31 are as follows:    2017 2016 2015  Statutory federal tax rate 35.0 % 35.0 % 35.0 %  Impact from Tax Reform (19.3) - -  State income taxes, net of federal benefit 1.4 2.6 6.3  Domestic manufacturing deduction (2.6) (2.5) -  Noncontrolling interests 0.3 1.4 (2.1)  Tax benefit of equity compensation (1.1) (1.0) 0.4  Other permanent differences 0.1 0.7 0.4  Effective tax rate 13.8 % 36.2 % 40.0 % 
Schedule of Deferred Tax Assets and Liabilities	Significant components of the company’s deferred tax assets and liabilities at December 31 are as follows (in thousands):     2017 2016  Deferred tax assets  Accrued expenses and allowances $ 16,322 $ 24,986  Inventories 4,109 11,805  Net operating loss carryforwards 33,693 48,920  Intangible assets - 14,779  Other 8,074 8,491  62,198 108,981  Less: valuation allowance (20,714) (33,427)  Total net deferred tax assets 41,484 75,554   Deferred tax liabilities  Property, plant and equipment (344,511) (519,977)  Intangible assets (1,292) -  Other (1,630) (3,952)  Total deferred tax liabilities (347,433) (523,929)  Net deferred tax liability $ (305,949) $ (448,375) 
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):     2017 2016 2015  Balance at January 1 $ 19,107 $ 15,991 $ 17,338  Increases related to current year tax positions 300 300 -  Increases related to prior year tax positions 271 5,452 81  Decreases related to prior year tax positions (863) (535) (719)  Settlements with taxing authorities (2,066) (2,101) (70)  Lapses in statute of limitations - - (639)  Balance at December 31 $ 16,749 $ 19,107 $ 15,991 

Equity-based Incentive Plans (T

Equity-based Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Equity-based Incentive Plans [Abstract]
Schedule of Restricted Stock Units Award Activity	A summary of the company’s RSU activity and outstanding RSUs as of December 31, 2017, are presented below (dollars in thousands except grant date fair value):   Weighted Aggregate  Number Average Grant Intrinsic Unrecognized  of RSUs Date Fair Value Value Compensation  Outstanding RSUs as of January 1, 2015 2,011,226 $19.85 $ 39,702 $ 25,171  Granted 1,589,309 $16.70  Vested (1,197,403) $18.13  Forfeited (124,428) $19.89  As of December 31, 2015 2,278,704 $18.55 $ 40,720 $ 27,615  Granted 852,063 $32.40  Vested (962,828) $22.76  Forfeited (139,922) $18.50  As of December 31, 2016 2,028,017 $22.38 $ 72,157 $ 29,086  Granted 828,955 $36.29  Vested (1,364,593) $18.50  Forfeited (78,737) $23.52  As of December 31, 2017 (nonvested) 1,413,642 $34.22 $ 60,970 $ 32,017 
Schedule of Stock Options Activity	A summary of the company’s stock option activity and certain information concerning the company’s outstanding options are presented below.     Weighted Weighted Average  Number Average Grant Date  of Options Exercise Price Fair Value  Outstanding options as of January 1, 2015 1,398,515 $14.62 $5.61  Exercised (753,159) $14.75 $5.75  Forfeited (49,411) $15.02 $5.87  As of December 31, 2015 595,945 $14.43 $5.41  Exercised (570,197) $14.41 $5.40  Forfeited (25,748) $14.96 $5.62  As of December 31, 2016 and 2017 - N/A N/A 
Schedule Of LTIP Awards	    Maximum  Shares That Award  Could Be Issued Earned Award Issued/Issuable   2013 LTIP Award:  Two-year performance period transition award 173,319 159,457 53,154 March 2015  66,252 March 2016  40,051 March 2017   Three-year performance period award 173,319 149,060 74,179 March 2016  37,441 March 2017  37,440 March 2018   2014 LTIP Award:  Three-year performance period award 204,741 204,741 68,249 March 2017  68,247 March 2018  68,245 March 2019  2015 LTIP Award:  Three-year performance period award 236,434 236,434 78,813 March 2018  78,812 March 2019  78,809 March 2020   2016 LTIP Award:  Three-year performance period award 324,469 * *   2017 LTIP Award:  Three-year performance period award 182,274 * *   Two-year performance period transition award 16,779 * *   One-year performance period transition award 28,379 25,541 8,514 March 2018  8,514 March 2019  8,513 March 2020 * Not yet earned as performance period not complete.

Derivative Financial Instrume27

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Financial Instruments
Schedule of Notional Amounts of Outstanding Derivative Positions	. The following summarizes the company’s futures contract commitments as of December 31, 2017 (MT represents metric tons):     Commodity Futures Long/Short Total  Aluminum Long 1,550 MT  Aluminum Short 1,775 MT  Copper Long 5,555 MT  Copper Short 26,091 MT  
Schedule of Derivatives Instruments Statements of Financial Performance and Financial Position	     Asset Derivatives Liability Derivatives  Balance sheet Fair Value Fair Value  location December 31, 2017 December 31, 2016 December 31, 2017 December 31, 2016  Derivative instruments designated  as fair value hedges -  Commodity futures Other current assets $ 1,211 $ 2,910 $ 5,364 $ 1,300   Derivative instruments not designated  as hedges -  Commodity futures Other current assets 1,579 1,150 5,142 783  Total derivative instruments $ 2,790 $ 4,060 $ 10,506 $ 2,083   The fair value of the above derivative instruments along with required margin deposit amounts with the same counterparty under master netting agreements totaled $5.6 million and $3.2 million at December 31, 2017 , and 2016 , respectively, and are reflected in other current assets in the consolidated balance sheets.  Note 7. Derivative Financial Instruments (Continued)         Amount of  Location of gain gain (loss) Location of gain Amount of gain  (loss) recognized recognized in Hedged items in (loss) recognized (loss) recognized in  in income on income on fair value hedge in income on income on related  derivatives derivatives relationships related hedged items hedged items  For the Year Ended  December 31, 2017   Derivatives in fair value  hedging relationships -  Commodity futures Costs of goods sold $ 5,763 Firm commitments Costs of goods sold $ 1,814  Inventory Costs of goods sold 3,008  Derivatives not designated $ 4,822  as hedging instruments -  Commodity futures Costs of goods sold $ (18,784)      For the Year Ended  December 31, 2016   Derivatives in fair value  hedging relationships -  Commodity futures Costs of goods sold $ 3,596 Firm commitments Costs of goods sold $ (3,901)  Inventory Costs of goods sold (538)  Derivatives not designated $ (4,439)  as hedging instruments -  Commodity futures Costs of goods sold $ (8,450)      For the Year Ended  December 31, 2015   Derivatives in fair value  hedging relationships -  Commodity futures Costs of goods sold $ (4,254) Firm commitments Costs of goods sold $ 2,084  Inventory Costs of goods sold 1,269  Derivatives not designated $ 3,353  as hedging instruments -  Commodity futures Costs of goods sold $ 16,261  

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Measurements
Schedule of assets and liabilities measured at fair value on a recurring basis	The following table sets forth financial assets and liabilities measured at fair value on a recurring basis in the consolidated balance sheet and the respective levels to which the fair value measurements are classified within the fair value hierarchy as of December 31 (in thousands):      Quoted Prices Significant  in Active Other Significant  Markets for Observable Unobservable  Identical Assets Inputs Inputs  Total (Level 1) (Level 2) (Level 3)  December 31, 2017  Commodity futures – financial assets $ 2,790 $ - $ 2,790 $ -  Commodity futures – financial liabilities 10,506 - 10,506 -   December 31, 2016  Commodity futures – financial assets $ 4,060 $ - $ 4,060 $ -  Commodity futures – financial liabilities 2,083 - 2,083 - 

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies
Schedule of Unconditional Purchase Obligations	The company’s commitments for these agreements with “take or pay” or other similar commitment provisions for the years ending December 31 are as follows (in thousands):    2018 $ 312,736  2019 116,779  2020 104,300  2021 90,894  2022 83,696  Thereafter 75,337  $ 783,742 

Leases (Table)

Leases (Table)	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	   2018 $ 16,036  2019 12,609  2020 9,496  2021 5,868  2022 4,051  Thereafter 5,754  $ 53,814 

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Information
Schedule of operating segment results	The company’s segment results are as follows (in thousands):     Metals Steel  For The Year Ended Steel Recycling Fabrication  December 31, 2017 Operations Operations Operations Other Eliminations Consolidated   Net Sales  External $ 6,613,944 $ 1,204,188 $ 823,630 $ 373,212 $ - $ 9,014,974  External Non-United States 317,819 205,853 151 - - 523,823  Other segments 243,646 1,402,963 644 2,299 (1,649,552) -  7,175,409 2,813,004 824,425 375,511 (1,649,552) 9,538,797  Operating income (loss) 1,098,630 71,052 87,295 (190,785) (1) 689 (2) 1,066,881  Income (loss) before income taxes 1,014,863 64,638 81,046 (226,001) 689 935,235  Depreciation and amortization 227,752 48,830 11,507 10,910 - 298,999  Capital expenditures 128,749 25,998 7,506 2,682 - 164,935   As of December 31, 2017   Assets $ 4,257,167 $ 1,011,298 $ 384,402 $ 1,334,361 (3) $ (131,496) (4) $ 6,855,732      Footnotes related to the year ended December 31, 2017, segment results (in millions):   (1) Corporate SG&A $ (49.4) (2) Gross profit increase from intra-company sales $ 0.7  Company-wide equity-based compensation (36.5)  Profit sharing (87.6)  Minnesota ironmaking operations (12.8)  Other, net (4.5)  $ (190.8)   (3) Cash and equivalents $ 1,003.2 (4) Elimination of intercompany receivables $ (106.1)  Accounts receivable 9.4 Elimination of intra-company debt (13.4)  Inventories 58.8 Other (12.0)  Income tax receivable 57.3 $ (131.5)  Property, plant and equipment, net 160.9  Intra-company debt 13.4  Other 31.4  $ 1,334.4         Note 13. Segment Information (Continued)     Metals Steel  For The Year Ended Steel Recycling Fabrication  December 31, 2016 Operations Operations Operations Other Eliminations Consolidated   Net Sales  External $ 5,399,275 $ 1,007,781 $ 700,852 $ 271,828 $ - $ 7,379,736  External Non-United States 235,436 161,560 189 188 - 397,373  Other segments 236,213 1,002,536 2,481 4,896 (1,246,126) -  5,870,924 2,171,877 703,522 276,912 (1,246,126) 7,777,109  Operating income (loss) 926,954 20,423 (5) 90,955 (301,116) (1) (9,250) (2) 727,966  Income (loss) before income taxes 836,818 8,378 (5) 82,776 (354,589) (9,250) 564,133  Depreciation and amortization 213,227 56,483 10,952 15,652 (205) 296,109  Capital expenditures 160,767 29,443 3,123 4,827 - 198,160   As of December 31, 2016   Assets $ 4,126,448 $ 1,038,946 $ 340,902 $ 1,054,448 (3) $ (137,012) (4) $ 6,423,732      Footnotes related to the year ended December 31, 2016, segment results (in millions):   (1) Corporate SG&A $ (48.9) (2) Gross profit decrease from intra-company sales $ (11.1)  Company-wide equity-based compensation (30.4) Non-cash asset impairment charges 1.8  Profit sharing (66.4) $ (9.3)  Minnesota ironmaking operations (15.8)  Minnesota ironmaking operations non-cash  asset impairment charges ($127.3 net  of eliminating amounts) (129.1)  Other, net (10.5)  $ (301.1)   (3) Cash and equivalents $ 775.7 (4) Elimination of intercompany receivables $ (112.3)  Accounts receivable 2.0 Elimination of intra-company debt (12.1)  Inventories 35.4 Other (12.6)  Income tax receivable 25.3 $ (137.0)  Property, plant and equipment, net 168.5  Intra-company debt 12.1  Other 35.4  $ 1,054.4   (5) Includes $5.5 million of non-cash goodwill  impairment charges.  Note 13. Segment Information (Continued)    Metals Steel  For The Year Ended Steel Recycling Fabrication  December 31, 2015 Operations Operations Operations Other Eliminations Consolidated   Net Sales  External $ 4,935,549 $ 1,249,061 $ 671,323 $ 283,965 $ - $ 7,139,898  External Non-United States 267,963 183,942 2,051 557 - 454,513  Other segments 218,963 904,713 25 30,325 (1,154,026) -  5,422,475 2,337,716 673,399 314,847 (1,154,026) 7,594,411  Operating income (loss) 403,216 (448,137) (3) 115,947 (148,784) (1) 4,974 (2) (72,784)  Income (loss) before income taxes 312,402 (465,426) (3) 108,795 (202,862) 4,974 (242,117)  Depreciation and amortization 205,827 65,640 9,587 13,746 (205) 294,595  Capital expenditures 71,752 21,874 3,395 17,480 - 114,501      Footnotes related to the year ended December 31, 2015, segment results (in millions):   (1) Corporate SG&A $ (37.8) (2) Gross profit increase from intra-company sales $ 5.0  Company-wide equity-based compensation (27.1)  Profit sharing (17.7)  Minnesota ironmaking operations (55.7)  Other, net (10.5)  $ (148.8)   (3) Includes $428.5 million of pretax non-cash asset  impairment charges. 

Transactions with Affiliated 32

Transactions with Affiliated Companies (Tables)	12 Months Ended
	Dec. 31, 2017
Transactions with Affiliated Companies [Abstract]
Schedule of Related Party Transactions	Transactions with Heidtman for the years ended December 31, are as follows (in thousands):    2017 2016 2015  Sales $ 150,981 $ 142,624 $ 162,742  Percentage of consolidated net sales 2% 2% 2%  Accounts receivable 19,354 20,737 30,627  Purchases 10,684 9,017 11,429  Accounts payable 663 494 431  The company also purchases and sells recycled and scrap metal with other smaller affiliated companies. These transactions are as follows (in thousands):    2017 2016 2015  Sales $ 23,603 $ 27,305 $ 24,436  Accounts receivable 3,068 5,483 3,645  Purchases 219,975 165,091 178,102  Accounts payable 15,020 12,576 6,199  

Condensed Consolidating Infor33

Condensed Consolidating Information (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Consolidating Information
Schedule of Condensed Consolidating Balance Sheets	   Condensed Consolidating Balance Sheets (in thousands)  Combined Consolidating Total  As of December 31, 2017 Parent Guarantors Non-Guarantors Adjustments Consolidated  Cash and equivalents $ 1,001,405 $ 20,441 $ 6,803 $ - $ 1,028,649  Accounts receivable, net 274,968 1,426,036 37,387 (869,554) 868,837  Inventories 685,103 752,151 91,890 (9,797) 1,519,347  Other current assets 73,748 16,005 5,962 (4,206) 91,509  Total current assets 2,035,224 2,214,633 142,042 (883,557) 3,508,342  Property, plant and equipment, net 859,419 1,618,438 198,047 - 2,675,904  Intangible assets, net - 225,503 31,406 - 256,909  Goodwill - 379,069 7,824 - 386,893  Other assets, including investments in subs 2,512,594 6,622 5,505 (2,497,037) 27,684  Total assets $ 5,407,237 $ 4,444,265 $ 384,824 $ (3,380,594) $ 6,855,732   Accounts payable $ 168,282 $ 316,676 $ 101,948 $ (97,458) $ 489,448  Accrued expenses 222,023 254,196 10,243 (136,186) 350,276  Current maturities of long-term debt 731 - 56,454 (28,390) 28,795  Total current liabilities 391,036 570,872 168,645 (262,034) 868,519  Long-term debt 2,326,466 - 169,799 (143,120) 2,353,145  Other liabilities (661,839) 869,196 24,868 95,535 327,760  Total liabilities 2,055,663 1,440,068 363,312 (309,619) 3,549,424   Redeemable noncontrolling interests - - 111,240 - 111,240   Common stock 644 1,727,859 14,908 (1,742,767) 644  Treasury stock (665,297) - - - (665,297)  Additional paid-in capital 1,141,534 128,076 797,196 (925,272) 1,141,534  Retained earnings (deficit) 2,874,693 1,148,262 (745,326) (402,936) 2,874,693  Total Steel Dynamics, Inc. equity 3,351,574 3,004,197 66,778 (3,070,975) 3,351,574  Noncontrolling interests - - (156,506) - (156,506)  Total equity 3,351,574 3,004,197 (89,728) (3,070,975) 3,195,068  Total liabilities and equity $ 5,407,237 $ 4,444,265 $ 384,824 $ (3,380,594) $ 6,855,732  Note 14. Condensed Consolidating Information (Continued)      Combined Consolidating Total  As of December 31, 2016 Parent Guarantors Non-Guarantors Adjustments Consolidated  Cash and equivalents $ 766,685 $ 54,677 $ 20,121 $ - $ 841,483  Accounts receivable, net 229,148 1,257,245 23,689 (780,298) 729,784  Inventories 587,319 639,148 58,696 (9,952) 1,275,211  Other current assets 45,049 36,062 4,447 (2,361) 83,197  Total current assets 1,628,201 1,987,132 106,953 (792,611) 2,929,675  Property, plant and equipment, net 899,370 1,679,751 208,094 - 2,787,215  Intangible assets, net - 251,919 32,058 - 283,977  Goodwill - 385,527 7,824 - 393,351  Other assets, including investments in subs 2,769,884 7,335 5,832 (2,753,537) 29,514  Total assets $ 5,297,455 $ 4,311,664 $ 360,761 $ (3,546,148) $ 6,423,732   Accounts payable $ 141,089 $ 265,764 $ 89,659 $ (101,316) $ 395,196  Accrued expenses 198,085 220,917 8,793 (113,808) 313,987  Current maturities of long-term debt 674 700 29,347 (27,089) 3,632  Total current liabilities 339,848 487,381 127,799 (242,213) 712,815  Long-term debt 2,324,298 - 168,566 (139,670) 2,353,194  Other liabilities (293,711) 1,219,444 42,482 (499,191) 469,024  Total liabilities 2,370,435 1,706,825 338,847 (881,074) 3,535,033   Redeemable noncontrolling interests - - 111,240 - 111,240   Common stock 641 1,727,859 14,908 (1,742,767) 641  Treasury stock (416,829) - - - (416,829)  Additional paid-in capital 1,132,749 128,076 779,678 (907,754) 1,132,749  Retained earnings (deficit) 2,210,459 748,904 (734,351) (14,553) 2,210,459  Total Steel Dynamics, Inc. equity 2,927,020 2,604,839 60,235 (2,665,074) 2,927,020  Noncontrolling interests - - (149,561) - (149,561)  Total equity 2,927,020 2,604,839 (89,326) (2,665,074) 2,777,459  Total liabilities and equity $ 5,297,455 $ 4,311,664 $ 360,761 $ (3,546,148) $ 6,423,732 
Schedule of Condensed Consolidating Statements of Operations	      Condensed Consolidating Statements of Operations (in thousands)   Combined Consolidating Total  For the year ended December 31, 2017 Parent Guarantors Non-Guarantors Adjustments Consolidated  Net sales $ 3,702,597 $ 10,366,526 $ 597,789 $ (5,128,115) $ 9,538,797  Costs of goods sold 2,994,257 9,399,996 577,205 (5,014,675) 7,956,783  Gross profit 708,340 966,530 20,584 (113,440) 1,582,014  Selling, general and administrative 221,736 293,161 20,493 (20,257) 515,133  Operating income (loss) 486,604 673,369 91 (93,183) 1,066,881  Interest expense, net of capitalized interest 73,521 57,622 12,901 (9,645) 134,399  Other (income) expense, net (2,305) (9,937) (156) 9,645 (2,753)  Income (loss) before income taxes and  equity in net income of subsidiaries 415,388 625,684 (12,654) (93,183) 935,235  Income taxes (benefit) (69,961) 226,327 5,266 (32,193) 129,439  485,349 399,357 (17,920) (60,990) 805,796  Equity in net income of subsidiaries 327,392 - - (327,392) -  Net loss attributable to noncontrolling interests - - 6,945 - 6,945  Net income (loss) attributable to Steel Dynamics, Inc. $ 812,741 $ 399,357 $ (10,975) $ (388,382) $ 812,741      Combined Consolidating Total  For the year ended December 31, 2016 Parent Guarantors Non-Guarantors Adjustments Consolidated  Net sales $ 3,037,801 $ 8,356,727 $ 388,071 $ (4,005,490) $ 7,777,109  Costs of goods sold 2,428,863 7,522,791 390,313 (3,899,722) 6,442,245  Gross profit (loss) 608,938 833,936 (2,242) (105,768) 1,334,864  Selling, general and administrative 196,442 281,071 16,103 (19,557) 474,059  Asset impairment charges 12,700 5,500 116,445 (1,806) 132,839  Operating income (loss) 399,796 547,365 (134,790) (84,405) 727,966  Interest expense, net of capitalized interest 71,182 72,420 10,874 (8,439) 146,037  Other (income) expense, net 14,200 (5,363) 520 8,439 17,796  Income (loss) before income taxes and  equity in net loss of subsidiaries 314,414 480,308 (146,184) (84,405) 564,133  Income taxes (benefit) 69,454 180,990 (15,825) (30,492) 204,127  244,960 299,318 (130,359) (53,913) 360,006  Equity in net loss of subsidiaries 137,155 - - (137,155) -  Net loss attributable to noncontrolling interests - - 22,109 - 22,109  Net income (loss) attributable to Steel Dynamics, Inc. $ 382,115 $ 299,318 $ (108,250) $ (191,068) $ 382,115   Note 14. Condensed Consolidating Information (Continued)     Combined Consolidating Total  For the year ended December 31, 2015 Parent Guarantors Non-Guarantors Adjustments Consolidated  Net sales $ 2,908,904 $ 8,132,043 $ 361,944 $ (3,808,480) $ 7,594,411  Costs of goods sold 2,515,621 7,646,411 420,281 (3,719,620) 6,862,693  Gross profit (loss) 393,283 485,632 (58,337) (88,860) 731,718  Selling, general and administrative 128,929 254,106 11,893 (18,926) 376,002  Asset impairment charges - 428,500 - - 428,500  Operating income (loss) 264,354 (196,974) (70,230) (69,934) (72,784)  Interest expense, net of capitalized interest 75,457 76,009 6,969 (4,485) 153,950  Other (income) expense, net 13,970 332 (3,404) 4,485 15,383  Income (loss) before income taxes and  equity in net loss of subsidiaries 174,927 (273,315) (73,795) (69,934) (242,117)  Income taxes (benefit) (124,626) 61,571 (4,627) (29,265) (96,947)  299,553 (334,886) (69,168) (40,669) (145,170)  Equity in net loss of subsidiaries (429,864) - - 429,864 -  Net loss attributable to noncontrolling interests - - 14,859 - 14,859  Net income (loss) attributable to Steel Dynamics, Inc. $ (130,311) $ (334,886) $ (54,309) $ 389,195 $ (130,311) 
Schedule of Condensed Consolidating Statements of Cash Flows	   Condensed Consolidating Statements of Cash Flows (in thousands)   Combined Consolidating Total  For the year ended December 31, 2017 Parent Guarantors Non-Guarantors Adjustments Consolidated   Net cash provided by (used in) operating activities $ 171,300 $ 594,279 $ (31,719) $ 5,746 $ 739,606  Net cash used in investing activities (62,534) (73,021) (8,301) 4,751 (139,105)  Net cash provided by (used in) financing activities 125,954 (555,494) 26,702 (10,497) (413,335)  Increase (decrease) in cash and equivalents 234,720 (34,236) (13,318) - 187,166  Cash and equivalents at beginning of period 766,685 54,677 20,121 - 841,483  Cash and equivalents at end of period $ 1,001,405 $ 20,441 $ 6,803 $ - $ 1,028,649       Combined Consolidating Total  For the year ended December 31, 2016 Parent Guarantors Non-Guarantors Adjustments Consolidated   Net cash provided by operating activities $ 326,216 $ 517,699 $ 6,057 $ 2,797 $ 852,769  Net cash used in investing activities (161,043) (140,027) (9,578) (2,245) (312,893)  Net cash provided by (used in) financing activities (35,365) (404,971) 15,463 (552) (425,425)  Increase (decrease) in cash and equivalents 129,808 (27,299) 11,942 - 114,451  Cash and equivalents at beginning of period 636,877 81,976 8,179 - 727,032  Cash and equivalents at end of period $ 766,685 $ 54,677 $ 20,121 $ - $ 841,483  Note 14. Condensed Consolidating Information (Continued)     Combined Consolidating Total  For the year ended December 31, 2015 Parent Guarantors Non-Guarantors Adjustments Consolidated   Net cash provided by operating activities $ 436,012 $ 594,437 $ 19,388 $ 3,788 $ 1,053,625  Net cash used in investing activities (64,457) (82,751) (15,703) 20,284 (142,627)  Net cash provided by (used in) financing activities 9 (511,400) (9,866) (24,072) (545,329)  Increase (decrease) in cash and equivalents 371,564 286 (6,181) - 365,669  Cash and equivalents at beginning of period 265,313 81,690 14,360 - 361,363  Cash and equivalents at end of period $ 636,877 $ 81,976 $ 8,179 $ - $ 727,032 

Quarterly Financial Informati34

Quarterly Financial Information (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information
Schedule of Quarterly Financial Information	    1 st Quarter 2 nd Quarter 3 rd Quarter 4 th Quarter  2017:  Net Sales $ 2,368,216 $ 2,390,720 $ 2,443,382 $ 2,336,479  Gross profit 472,154 392,518 396,518 320,824  Operating income 334,566 265,353 271,015 195,947  Net income 198,666 152,947 151,012 303,171  Net income attributable to Steel Dynamics, Inc. 200,817 153,933 153,258 304,733  Earnings per share:  Basic 0.83 0.64 0.64 1.28  Diluted 0.82 0.63 0.64 1.28   2016:  Net Sales $ 1,741,301 $ 2,023,902 $ 2,101,310 $ 1,910,596  Gross profit 236,036 380,383 408,503 309,942  Operating income 131,965 256,122 283,855 56,024  Net income 61,318 140,443 154,413 3,832  Net income attributable to Steel Dynamics, Inc. 62,737 141,969 157,397 20,012  Earnings per share:  Basic 0.26 0.58 0.65 0.08  Diluted 0.26 0.58 0.64 0.08 

Description of the Business a35

Description of the Business and Significant Accounting Policies (Segments) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)segmentitem	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Reporting Information
Workforce represented by collective bargaining agreements (as a percent)	9.00%
Number of collective bargaining agreements that expire | item	5
Workforce Subject To Collective Bargaining Arrangements Subject to Expire Percent	0.40%
Number of locations subject to collective bargaining agreements that expire | item	1
Impairment charges		$ 132,839	$ 428,500
Segment Reporting Information
Number of reporting segments | segment	3
Steel Operations
Segment Reporting Information
Percentage of external net sales	72.00%	72.00%	69.00%
Metals Recycling Operations
Segment Reporting Information
Percentage of external net sales	15.00%	15.00%	19.00%
Steel Fabrication Operations
Segment Reporting Information
Percentage of external net sales	9.00%	9.00%	9.00%
Mining Resources
Segment Reporting Information
Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions	83.00%	82.00%
Business Combination, Consideration Transferred	$ 15,100
Minnesota ironmaking operations
Segment Reporting Information
Impairment charges	127,300	$ 5,500	$ 428,500
Minnesota ironmaking operations | Parent [Member]
Segment Reporting Information
Impairment charges	72,900
Minnesota ironmaking operations | Noncontrolling Interests
Segment Reporting Information
Impairment charges	$ 13,100

Description of the Business a36

Description of the Business and Summary of Significant Accounting Policies (Inventories) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Description of the Business and Significant Accounting Policies
Raw materials	$ 675,715	$ 515,924
Supplies	374,515	383,134
Work in progress	128,565	103,606
Finished goods	340,552	272,547
Total inventories	$ 1,519,347	$ 1,275,211

Description of the Business a37

Description of the Business and Summary of Significant Accounting Policies (Property, Plant and Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, plant and equipment
Depreciation expense	$ 263,700	$ 260,600	$ 263,200
Property, plant and equipment	5,165,508	5,066,989
Less accumulated depreciation	2,489,604	2,279,774
Property, Plant and Equipment, Net, Total	2,675,904	2,787,215
Land and improvements
Property, plant and equipment
Property, plant and equipment	314,854	311,005
Buildings and improvements
Property, plant and equipment
Property, plant and equipment	$ 723,504	709,809
Buildings and improvements | Minimum
Property, plant and equipment
Property, plant and equipment useful life	10 years
Buildings and improvements | Maximum
Property, plant and equipment
Property, plant and equipment useful life	40 years
Plant, machinery and equipment
Property, plant and equipment
Property, plant and equipment	$ 4,035,717	3,975,560
Plant, machinery and equipment | Minimum
Property, plant and equipment
Property, plant and equipment useful life	3 years
Plant, machinery and equipment | Maximum
Property, plant and equipment
Property, plant and equipment useful life	20 years
Construction in progress
Property, plant and equipment
Property, plant and equipment	$ 91,433	$ 70,615

Description of the Business a38

Description of the Business and Summary of Significant Accounting Policies (Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 526,777	$ 578,653
Less accumulated amortization	269,868	294,676
Intangible Assets, Net (Excluding Goodwill), Total	256,909	283,977
Amortization of Intangible Assets	29,193	28,765	$ 24,180
Estimated amortization expense
2,018	26,910
2,019	24,823
2,020	22,629
2,021	20,840
2,022	19,231
Thereafter	142,476
Total	$ 256,909
Impairment of Long-Lived Tangible and Definite-Lived Intangible Assets
Assets held for sale, asset impairment charge		10,300
Asset impairment charges		132,839	428,500
Weighted average
Finite-Lived Intangible Assets [Line Items]
Useful Life	20 years
Minnesota ironmaking operations
Impairment of Long-Lived Tangible and Definite-Lived Intangible Assets
Asset impairment charges	$ 127,300	5,500	$ 428,500
Minnesota ironmaking operations | Noncontrolling Interests
Impairment of Long-Lived Tangible and Definite-Lived Intangible Assets
Asset impairment charges	13,100
Minnesota ironmaking operations | Parent [Member]
Impairment of Long-Lived Tangible and Definite-Lived Intangible Assets
Asset impairment charges	72,900
Customer and scrap generator relationships
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 394,062	446,688
Customer and scrap generator relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life	5 years
Customer and scrap generator relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life	25 years
Customer and scrap generator relationships | Weighted average
Finite-Lived Intangible Assets [Line Items]
Useful Life	21 years
Trade names
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 130,550	130,550
Trade names | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life	15 years
Trade names | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life	25 years
Trade names | Weighted average
Finite-Lived Intangible Assets [Line Items]
Useful Life	18 years
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 2,165	1,415
Other Intangible Assets [Member] | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life	3 years
Other Intangible Assets [Member] | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life	5 years
Other Intangible Assets [Member] | Weighted average
Finite-Lived Intangible Assets [Line Items]
Useful Life	4 years
Other current assets
Impairment of Long-Lived Tangible and Definite-Lived Intangible Assets
Assets held for sale	$ 8,700	$ 29,300

Description of the Business a39

Description of the Business and Significant Accounting Policies (Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill
Goodwill	$ 386,893	$ 393,351
Compensation expense for stock options	36,600	30,400	$ 27,100
Steel Operations | Columbus Flat Roll Division
Goodwill
Goodwill	19,682	19,682
Steel Operations | The Techs
Goodwill
Goodwill	142,783	142,783
Steel Operations | Vulcan Steel Products [Member]
Goodwill
Goodwill	7,824	7,824
Steel Operations | Roanoke Bar Division
Goodwill
Goodwill	29,041	29,041
Metals Recycling Operations | Butler Flat Roll Division, Structural and Rail Division, and Engineered Bar Division
Goodwill
Goodwill	95,000	95,000
Metals Recycling Operations | OmniSource
Goodwill
Goodwill	90,638	97,096
Goodwill, Impairment Loss	5,500	341,300
Goodwill decrease due to tax benefit related to the normal amortization of the component	6,500
Goodwill, Impaired, Accumulated Impairment Loss	346,800
Indefinite-lived intangible assets impairment charge		68,500
Steel Fabrication Operations | New Millennium Building Systems
Goodwill
Goodwill	$ 1,925	$ 1,925

Description of the Business a40

Description of the Business and Significant Accounting Policies (Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Income (Numerator)
Basic earnings per share - net income (in dollars)	$ 304,733	$ 153,258	$ 153,933	$ 200,817	$ 20,012	$ 157,397	$ 141,969	$ 62,737	$ 812,741	$ 382,115	$ (130,311)
5.125% convertible senior notes, net of tax											$ (130,311)
Diluted earnings per share - net income (in dollars)									$ 812,741	$ 382,115
Weighted average common shares outstanding (in shares)
Weighted average common shares outstanding - basic (in shares)									240,132	243,576	242,017
Dilutive common share equivalents (in shares)									1,649	1,722
5.125% convertible senior notes, net of tax											242,017
Weighted average common shares outstanding - diluted (in shares)									241,781	245,298	242,017
Per Share Amount
Basic (in dollars per share)	$ 1.28	$ 0.64	$ 0.64	$ 0.83	$ 0.08	$ 0.65	$ 0.58	$ 0.26	$ 3.38	$ 1.57	$ (0.54)
Diluted (in dollars per share)	$ 1.28	$ 0.64	$ 0.63	$ 0.82	$ 0.08	$ 0.64	$ 0.58	$ 0.26	$ 3.36	$ 1.56	$ (0.54)
Employee Stock Option
Antidilutive securities excluded from computation of earnings per share amount
Antidilutive common share equivalents excluded from computation of earnings per share amount (in shares)											1,500

Description of the Business a41

Description of the Business and Summary of Significant Accounting Policies - (Concentration of Credit Risk) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounts receivable | Credit risk
Concentration of credit risk
Percentage of consolidated net accounts receivable from related party	2.00%	3.00%

Acquisitions (Narrative) (Detai

Acquisitions (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 01, 2016
Acquisition
Purchase price paid in cash		$ 6,192	$ 123,351	$ 45,000
Vulcan
Acquisition
Business Acquisition, Percentage of Voting Interests Acquired					100.00%
Purchase price paid in cash	$ 113,000

Long-Term Debt - By Issue (Deta

Long-Term Debt - By Issue (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Long Term Debt
Total debt	$ 2,408,852		$ 2,386,791
Less debt issuance costs	26,912		29,965
Total amounts outstanding	2,381,940		2,356,826
Less current maturities	28,795		3,632
Long-term debt	2,353,145		2,353,194
5.125% senior notes due 2021
Long Term Debt
Total debt	700,000		700,000
Total amounts outstanding	$ 700,000
Stated interest rate	5.125%
5 1/4% Senior Notes due 2023
Long Term Debt
Total debt	$ 400,000		400,000
Total amounts outstanding	$ 400,000
Stated interest rate	5.25%
5.500% senior notes due 2024
Long Term Debt
Total debt	$ 500,000		500,000
Total amounts outstanding	$ 500,000
Stated interest rate	5.50%
4.125% Senior Note due 2025 [Member]
Long Term Debt
Total debt	$ 350,000
Total amounts outstanding	$ 350,000
Stated interest rate	4.125%	4.125%
Senior Notes 5.000 Percent Due 2026 [Member]
Long Term Debt
Total debt	$ 400,000		400,000
Total amounts outstanding	$ 400,000
Stated interest rate	5.00%
6 3/8% Senior Notes, due 2022
Long Term Debt
Total debt			350,000
Stated interest rate	6.375%
6 1/8% senior notes, due 2019
Long Term Debt
Stated interest rate	6.125%
Other obligations
Long Term Debt
Total debt	$ 58,852		$ 36,791

Long-Term Debt - Financing Acti

Long-Term Debt - Financing Activity (Details) - USD ($)	1 Months Ended			3 Months Ended	12 Months Ended
	Oct. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Long Term Debt
Repayments of debt					$ 609,914,000	$ 728,993,000	$ 625,924,000
5.125% senior notes due 2021
Long Term Debt
Stated interest rate					5.125%
6 3/8% Senior Notes, due 2022
Long Term Debt
Stated interest rate					6.375%
Redemption price of debt instrument (as a percent)	103.188%	103.563%
Debt Instrument, Repurchased Face Amount	$ 167,100,000	$ 182,900,000
5 1/4% Senior Notes due 2023
Long Term Debt
Stated interest rate					5.25%
5.500% senior notes due 2024
Long Term Debt
Stated interest rate					5.50%
Senior Notes 5.000 Percent Due 2026 [Member]
Long Term Debt
Debt Instrument, Face Amount					$ 400,000,000
Stated interest rate					5.00%
6 1/8% senior notes, due 2019
Long Term Debt
Debt Instrument, Face Amount					$ 400,000,000
Stated interest rate					6.125%
Associated premiums and related expenses recorded				$ 16,500,000
Redemption price of debt instrument (as a percent)			103.388%
Repayments of debt			$ 266,300,000
7 5/8% senior notes, due 2020
Long Term Debt
Stated interest rate							7.625%
Redemption price of debt instrument (as a percent)						103.813%
Repayments of debt						$ 350,000,000,000
Expenses recorded related to tender offer and early payoff of Senior Notes related to tender premiums, unamortized debt issuance cost write-off, and tender expenses							$ 16,700,000
Senior Notes Due 2016 [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)			103.063%
Repayments of debt			$ 133,700,000
Senior term loan
Long Term Debt
Repayments of debt			228,100,000	$ 228,100,000
Expenses recorded related to tender offer and early payoff of Senior Notes related to tender premiums, unamortized debt issuance cost write-off, and tender expenses			$ 16,500,000
4.125% Senior Note due 2025 [Member]
Long Term Debt
Debt Instrument, Face Amount		$ 350,000,000
Stated interest rate		4.125%			4.125%
Expenses recorded related to tender offer and early payoff of Senior Notes related to tender premiums, unamortized debt issuance cost write-off, and tender expenses					$ 14,600,000

Long-Term Debt - Senior Secured

Long-Term Debt - Senior Secured Credit Facility (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Long Term Debt
Repayments of debt	$ 609,914	$ 728,993	$ 625,924
Unpaid principal balance payment	703,708
Senior secured revolving credit facility
Long Term Debt
Maximum borrowing capacity of credit facility	1,200,000
Additional amount by which facility size can be increased	750,000
Availability on the senior secured revolver	1,200,000
Outstanding letters of credit and other obligations which reduce availability	$ 11,900
Consolidated interest coverage ratio	10.75
Leverage ratio	1.35
Senior secured revolving credit facility | Minimum
Long Term Debt
Unused commitment fee (as a percent)	0.225%
Consolidated interest coverage ratio	2.50
Leverage ratio	3.50
Senior secured revolving credit facility | Minimum | LIBOR
Long Term Debt
Interest rate added to the base rate (as a percent)	1.00%
Senior secured revolving credit facility | Maximum
Long Term Debt
Unused commitment fee (as a percent)	0.375%
Leverage ratio	5
Senior secured revolving credit facility | Maximum | LIBOR
Long Term Debt
Interest rate added to the base rate (as a percent)	2.00%
Senior secured revolving credit facility | Maximum | Prime
Long Term Debt
Interest rate added to the base rate (as a percent)	1.00%

Long-Term Debt - Senior Unsecur

Long-Term Debt - Senior Unsecured Notes (Details) - USD ($) $ in Thousands	1 Months Ended			12 Months Ended
	Oct. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2017
Long Term Debt
Outstanding Balance			$ 2,356,826	$ 2,381,940
Senior Notes | Maximum
Long Term Debt
Maximum redemption of debt instrument (as a percent)				35.00%
5.125% senior notes due 2021
Long Term Debt
Outstanding Balance				$ 700,000
Stated interest rate				5.125%
5.125% senior notes due 2021 | Debt Instrument, Redemption, Period Three [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				101.281%
5.125% senior notes due 2021 | Debt Instrument, Redemption, Period Four [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				100.00%
6 3/8% Senior Notes, due 2022
Long Term Debt
Stated interest rate				6.375%
Redemption price of debt instrument (as a percent)	103.188%	103.563%
5 1/4% Senior Notes due 2023
Long Term Debt
Outstanding Balance				$ 400,000
Stated interest rate				5.25%
5 1/4% Senior Notes due 2023 | Debt Instrument, Redemption, Period Two [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				102.625%
5 1/4% Senior Notes due 2023 | Debt Instrument, Redemption, Period Three [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				101.75%
5 1/4% Senior Notes due 2023 | Debt Instrument, Redemption, Period Four [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				100.875%
5 1/4% Senior Notes due 2023 | Debt Instrument, Redemption, Period Five [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				100.00%
5.500% senior notes due 2024
Long Term Debt
Outstanding Balance				$ 500,000
Stated interest rate				5.50%
5.500% senior notes due 2024 | Debt Instrument, Redemption, Period Two [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				102.75%
5.500% senior notes due 2024 | Debt Instrument, Redemption, Period Three [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				101.833%
5.500% senior notes due 2024 | Debt Instrument, Redemption, Period Four [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				100.917%
5.500% senior notes due 2024 | Debt Instrument, Redemption, Period Five [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				100.00%
4.125% Senior Note due 2025 [Member]
Long Term Debt
Outstanding Balance				$ 350,000
Stated interest rate		4.125%		4.125%
4.125% Senior Note due 2025 [Member] | Debt Instrument, Redemption, Period One [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				104.125%
4.125% Senior Note due 2025 [Member] | Debt Instrument, Redemption, Period Two [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				102.063%
4.125% Senior Note due 2025 [Member] | Debt Instrument, Redemption, Period Three [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				101.031%
4.125% Senior Note due 2025 [Member] | Debt Instrument, Redemption, Period Four [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				100.00%
Senior Notes 5.000 Percent Due 2026 [Member]
Long Term Debt
Outstanding Balance				$ 400,000
Stated interest rate				5.00%
Senior Notes 5.000 Percent Due 2026 [Member] | Debt Instrument, Redemption, Period One [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				105.00%
Senior Notes 5.000 Percent Due 2026 [Member] | Debt Instrument, Redemption, Period Two [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				102.50%
Senior Notes 5.000 Percent Due 2026 [Member] | Debt Instrument, Redemption, Period Three [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				101.667%
Senior Notes 5.000 Percent Due 2026 [Member] | Debt Instrument, Redemption, Period Four [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				100.833%
Senior Notes 5.000 Percent Due 2026 [Member] | Debt Instrument, Redemption, Period Five [Member]
Long Term Debt
Redemption price of debt instrument (as a percent)				100.00%
6 1/8% senior notes, due 2019
Long Term Debt
Stated interest rate				6.125%
Redemption price of debt instrument (as a percent)			103.388%

Long-Term Debt - Other Secured

Long-Term Debt - Other Secured Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Long Term Debt
Outstanding principal balance	$ 2,408,852	$ 2,386,791
Minnesota Economic Development State Loans
Long Term Debt
Stated interest rate	3.50%
Outstanding principal balance	$ 20,600	22,300
Interest rate percent after February 2017	5.00%
Electric Utility Development Loans
Long Term Debt
Stated interest rate	8.10%
Outstanding principal balance	$ 3,600	4,200
Senior secured revolving credit facility
Long Term Debt
Unused stand-by letter of credit	1,200,000
Maximum borrowing capacity of credit facility	1,200,000
Standby letters of credit | Electric Utility Development Loans
Long Term Debt
Unused stand-by letter of credit	$ 3,000
Revolving credit facility entered into by a controlled subsidiary
Long Term Debt
Interest rate on debt instrument	3.90%
Maximum borrowing capacity of credit facility	$ 40,000
Borrowings outstanding	$ 25,700	0
Secured Debt [Member]
Long Term Debt
Stated interest rate	6.00%
Outstanding principal balance	$ 8,900	$ 9,500

Long-Term Debt - Outstanding De

Long-Term Debt - Outstanding Debt Maturities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Maturities of outstanding debt
2,018	$ 28,795
2,019	3,291
2,020	3,492
2,021	703,708
2,022	3,174
Thereafter	1,666,392
Total debt	2,408,852	$ 2,386,791
Interest costs
Interest costs incurred	136,100	148,500	$ 154,400
Interest costs incurred capitalized	1,700	2,500	457,000,000
Cash paid for interest	$ 135,381	$ 150,679	$ 160,190

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statutory federal tax rate			35.00%	35.00%	35.00%
Income Tax Expense (Benefit)			$ 129,439	$ 204,127	$ (96,947)
Income Tax Expense (Benefit) Due to Tax Reform	$ 180,600		(180,600)
Deferred Tax Assets, Valuation Allowance	20,714		20,714	$ 33,427
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			12,700
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	12,500		12,500
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense			85
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	4,800		4,800
Scenario, Forecast [Member]
Statutory federal tax rate		21.00%
Minimum
Income Tax Examination, Estimate of Possible Loss			0
Maximum
Income Tax Examination, Estimate of Possible Loss			3,300
Domestic Tax Authority [Member]
Income Tax Expense (Benefit) Due to Tax Reform			182,500
Operating Loss Carryforwards	$ 93,200		93,200
State and Local Jurisdiction [Member]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			4,300
Foreign Tax Authority [Member]
Income Tax Expense (Benefit) Due to Tax Reform			$ 1,900

Income Taxes (Schedule of Compo

Income Taxes (Schedule of Components of Income Tax Expense (Benefit) ) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes
Current income tax expense	$ 269,387	$ 153,176	$ 6,391
Deferred income tax expense (benefit)	(139,948)	50,951	(103,338)
Total income tax expense (benefit)	$ 129,439	$ 204,127	$ (96,947)

Income Taxes (Schedule of Effec

Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes
Statutory federal tax rate	35.00%	35.00%	35.00%
Impact from Tax Reform	(19.30%)
State income taxes, net of federal benefit	1.40%	2.60%	6.30%
Domestic manufacturing deduction	(2.60%)	(2.50%)
Noncontrolling interests	0.30%	1.40%	(2.10%)
Tax benefit of equity based compensation	(1.10%)	(1.00%)	0.40%
Other permanent differences	0.10%	0.70%	0.40%
Effective tax rate	13.80%	36.20%	40.00%

Income Taxes (Schedule of Defer

Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Accrued expenses and allowances	$ 16,322	$ 24,986
Inventories	4,109	11,805
Net operating loss carryforwards	33,693	48,920
Intangible Assets		14,779
Other	8,074	8,491
Subtotal	62,198	108,981
Less: valuation allowance	(20,714)	(33,427)
Total net deferred tax assets	41,484	75,554
Deferred tax liabilities
Property, plant and equipment	(344,511)	(519,977)
Intangible assets	(1,292)
Other	(1,630)	(3,952)
Total deferred tax liabilities	(347,433)	(523,929)
Net deferred tax liability	$ (305,949)	$ (448,375)

Income Taxes (Schedule of Unrec

Income Taxes (Schedule of Unrecognized Tax Benefits Roll Forward) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes
Unrecognized Tax Benefits, Beginning Balance	$ 19,107	$ 15,991	$ 17,338
Increases related to current year tax positions	300	300
Increases related to prior year tax positions	271	5,452	81
Decreases related to prior year tax positions	(863)	(535)	(719)
Settlements with taxing authorities	(2,066)	(2,101)	(70)
Lapses in statute of limitations			(639)
Unrecognized Tax Benefits, Ending Balance	$ 16,749	$ 19,107	$ 15,991

Shareholders_ Equity (Details)

Shareholders’ Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shareholders’ Equity
Dividends, Common Stock, Cash	$ 148,231	$ 136,472	$ 133,227
Common Stock, Dividends, Per Share, Declared	$ 0.62	$ 0.56	$ 0.55
Payments of Ordinary Dividends, Common Stock	$ 145,565	$ 135,767	$ 127,569
Stock Repurchase Program, Authorized Amount	$ 450,000
Share repurchases (in shares)	7,400	732
Share repurchases	$ 252,242	$ 25,034
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 172,700

Equity-based Incentive Plans (2

Equity-based Incentive Plans (2015 Equity Incentive Plan ) (Details)	12 Months Ended
	Dec. 31, 2017shares	Dec. 31, 2016shares	Dec. 31, 2015shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Retirement Eligible Age For Vesting Of Awards	59 years 6 months
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	5 years
Additional number of shares authorized for issuance		12,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	5,300,000
Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	100.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years
Equity Incentive 2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Share Limit Against Which Full Value Awards Will Be Counted	2.09
Deferred Stock Units (DSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	34,000	60,000	51,000
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	200,000	86,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	828,955	852,063	1,589,309

Equity-based Incentive Plans (R

Equity-based Incentive Plans (Restricted Stock Units) (Details) - Restricted Stock Units (RSUs) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of RSUs
Outstanding	2,028,017	2,278,704	2,011,226
Granted	828,955	852,063	1,589,309
Vested	(1,364,593)	(962,828)	(1,197,403)
Forfeited	(78,737)	(139,922)	(124,428)
Outstanding	1,413,642	2,028,017	2,278,704
Weighted Average Grant Date Fair Value
Outstanding	$ 22.38	$ 18.55	$ 19.85
Granted	36.29	32.40	16.70
Vested	18.50	22.76	18.13
Forfeited	23.52	18.50	19.89
Outstanding	$ 34.22	$ 22.38	$ 18.55
Aggregate Intrinsic Value
Outstanding	$ 60,970	$ 72,157	$ 40,720	$ 39,702
Unrecognized Compensation
Outstanding	$ 32,017	29,086	27,615	$ 25,171
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Weighted average remaining life	1 year 4 months 13 days
Fair value of instruments vested during the period	$ 58,800	$ 34,300	$ 21,400
Total shares withheld	457,000	338,000	427,000

Equity-based Incentive Plans (S

Equity-based Incentive Plans (Stock Options) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Options
Outstanding	0
Employee Stock Option
Number of Options
Outstanding		595,945	1,398,515
Exercised		(570,197)	(753,159)
Forfeited		(25,748)	(49,411)
Outstanding			595,945
Weighted Average Exercise Price
Outstanding		$ 14.43	$ 14.62
Exercised		14.41	14.75
Forfeited		14.96	15.02
Outstanding			14.43
Weighted Average Grant Date Fair Value
Outstanding		5.41	5.61
Exercised		5.40	5.75
Forfeited		$ 5.62	5.87
Outstanding			$ 5.41
Unrecognized Compensation
Outstanding	$ 0
Aggregate intrinsic value	$ 5.6	$ 4

Equity-based Incentive Plans (L

Equity-based Incentive Plans (Long-Term Incentive Compensation Program) (Details) - Senior Executive Officers	12 Months Ended
	Dec. 31, 2017shares
Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards earned as percentage of specified compensation	0.00%
Performance Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards earned as percentage of specified compensation	100.00%
2013 Award | Two-year performance period transition award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	173,319
Award Earned	159,457
2013 Award | Two-year performance period transition award | Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	53,154
2013 Award | Two-year performance period transition award | Performance/Service period two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	66,252
2013 Award | Two-year performance period transition award | Performance/Service period three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	40,051
2013 Award | Three-year performance period award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	173,319
Award Earned	149,060
2013 Award | Three-year performance period award | Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	74,179
2013 Award | Three-year performance period award | Performance/Service period two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	37,441
2013 Award | Three-year performance period award | Performance/Service period three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	37,440
2014 Award | Three-year performance period award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	204,741
Award Earned	204,741
2014 Award | Three-year performance period award | Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	68,249
2014 Award | Three-year performance period award | Performance/Service period two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	68,247
2014 Award | Three-year performance period award | Performance/Service period three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	68,245
2015 Award | Three-year performance period award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	236,434
Award Earned	236,434
2015 Award | Three-year performance period award | Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	78,813
2015 Award | Three-year performance period award | Performance/Service period two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	78,812
2015 Award | Three-year performance period award | Performance/Service period three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	78,809
2016 Award | Three-year performance period award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	324,469
2017 Award | One-year performance period transition award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	28,379
Award Earned	25,541
2017 Award | One-year performance period transition award | Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	8,514
2017 Award | One-year performance period transition award | Performance/Service period two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	8,514
2017 Award | One-year performance period transition award | Performance/Service period three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	8,513
2017 Award | Two-year performance period transition award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	16,779
2017 Award | Three-year performance period award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	182,274

Equity-based Incentive Plans 59

Equity-based Incentive Plans (2013 Executive Incentive Compensation Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional number of shares authorized for issuance		12,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	5,300,000
Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years
Executive Incentive Compensation Plan 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			2,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	2,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	117,000	117,000
Award Market Value	$ 5.3	$ 4
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years

Equity-based Incentive Plans 60

Equity-based Incentive Plans (2014 Employee Stock Purchase Plan) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 36,600,000	$ 30,400,000	$ 27,100,000
Employee Stock Purchase Plan 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum annual allowable payroll deduction per employee	$ 10,400
Employer's matching contribution percentage of employees' payroll deductions	10.00%
Allocated Share-based Compensation Expense	$ 558,000	$ 514,000	$ 468,000

Derivative Financial Instrume61

Derivative Financial Instruments (Narrative) (Details) - Commodity contract - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other current assets | Futures
Commodity contract commitments
Fair value of derivatives including required margin deposits	$ 5,600	$ 3,200
Designated as hedging instrument
Gains or losses on derivative instruments, statement of income
Ineffectiveness - amount of gain (loss) recognized in income on related hedged items		(191)
Gain (loss) excluded from hedge effectiveness testing		$ (652)
Designated as hedging instrument | Futures
Gains or losses on derivative instruments, statement of income
Ineffectiveness - amount of gain (loss) recognized in income on related hedged items	(3)		$ 90
Gain (loss) excluded from hedge effectiveness testing	$ (938)		$ (991)

Derivative Financial Instrume62

Derivative Financial Instruments (Schedule of Notional Amounts of Outstanding Derivative Positions) (Details)	12 Months Ended
	Dec. 31, 2017T
Aluminum | Long
Derivative [Line Items]
Commodity contract (in MT/Lbs)	1,550
Aluminum | Short
Derivative [Line Items]
Commodity contract (in MT/Lbs)	1,775
Copper | Long
Derivative [Line Items]
Commodity contract (in MT/Lbs)	5,555
Copper | Short
Derivative [Line Items]
Commodity contract (in MT/Lbs)	26,091

Derivative Financial Instrume63

Derivative Financial Instruments (Schedule of Derivatives Instruments Statements of Financial Performance and Financial Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commodity futures, asset derivatives	$ 2,790	$ 4,060
Commodity futures, liability derivatives	10,506	2,083
Futures | Commodity contract | Designated as hedging instrument | Other current assets
Commodity futures, asset derivatives	1,211	2,910
Commodity futures, liability derivatives	5,364	1,300
Futures | Commodity contract | Not designated as hedging instrument | Other current assets
Commodity futures, asset derivatives	1,579	1,150
Commodity futures, liability derivatives	$ 5,142	$ 783

Derivative Financial Instrume64

Derivative Financial Instruments (Schedule of Derivatives Instruments Statements of Financial Position) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Designated as hedging instrument
Amount of gain (loss) recognized in income on related hedged items	$ 4,822	$ (4,439)	$ 3,353
Designated as hedging instrument | Firm commitments | Cost of goods sold
Amount of gain (loss) recognized in income on related hedged items	1,814	(3,901)	2,084
Designated as hedging instrument | Inventory | Cost of goods sold
Amount of gain (loss) recognized in income on related hedged items	3,008	(538)	1,269
Futures | Designated as hedging instrument | Commodity contract | Cost of goods sold
Amount of gain (loss) recognized in income on derivatives	5,763	3,596	(4,254)
Futures | Not designated as hedging instrument | Commodity contract | Cost of goods sold
Amount of gain (loss) recognized in income on derivatives	$ (18,784)	$ (8,450)	$ 16,261

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets and liabilities subject to fair value measurements
Commodity futures - financial assets	$ 2,790	$ 4,060
Commodity futures - financial liabilities	10,506	2,083
Fair value of long-term debt, including current maturities	2,500,000
Outstanding Balance	2,381,940	2,356,826
Recurring | Commodity contract | Futures
Assets and liabilities subject to fair value measurements
Commodity futures - financial assets	2,790	4,060
Commodity futures - financial liabilities	10,506	2,083
Recurring | Level 2 | Commodity contract | Futures
Assets and liabilities subject to fair value measurements
Commodity futures - financial assets	2,790	4,060
Commodity futures - financial liabilities	$ 10,506	$ 2,083

Commitments and Contingencies66

Commitments and Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Commitments and Contingencie [Line Items]
Construction in Progress Expenditures Incurred but Not yet Paid	$ 74.7
Inventories [Member]
Commitments and Contingencie [Line Items]
Purchase Commitments Physical Commodity Requirements Utilization Period	3 years
Inventories [Member] | Maximum
Commitments and Contingencie [Line Items]
Purchase Commitments Commodity Transportation Requirements Period	5 years
Purchase Commitments Commodity Transportation Requirements Period For Products	11 years

Retirement Plans (Details)

Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Defined Contribution Plan, Cost Recognized	$ 92.5	$ 64.7	$ 21
Profit sharing component	$ 80.7	$ 59.3	$ 17.7
Percentage of employer's profit sharing contribution	8.00%	8.00%	8.00%
Employer's contribution to profit sharing plans for eligable employees	$ 64.5	$ 47.5	$ 14.1

Leases (Narrative) (Details)

Leases (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases [Abstract]
Payments for Rent	$ 18.9	$ 15.1	$ 15.1

Leases (Schedule of Future Mini

Leases (Schedule of Future Minimum Rental Payments for Operating Leases) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Leases [Abstract]
2,018	$ 16,036
2,019	12,609
2,020	9,496
2,021	5,868
2,022	4,051
Thereafter	5,754
Future Minimum Payments Due, Total	$ 53,814

Segment Information - Results (

Segment Information - Results (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information
Net sales	$ 2,336,479	$ 2,443,382	$ 2,390,720	$ 2,368,216	$ 1,910,596	$ 2,101,310	$ 2,023,902	$ 1,741,301	$ 9,538,797	$ 7,777,109	$ 7,594,411
Operating income (loss)	195,947	$ 271,015	$ 265,353	$ 334,566	56,024	$ 283,855	$ 256,122	$ 131,965	1,066,881	727,966	(72,784)
Income (loss) before income taxes									935,235	564,133	(242,117)
Depreciation and amortization									298,999	296,109	294,595
Capital expenditures									164,935	198,160	114,501
Assets	6,855,732				6,423,732				6,855,732	6,423,732
U.S.
Segment Reporting Information
Net sales									9,014,974	7,379,736	7,139,898
Non-U.S.
Segment Reporting Information
Net sales									523,823	397,373	454,513
Steel Operations
Segment Reporting Information
Net sales									7,175,409	5,870,924	5,422,475
Operating income (loss)									1,098,630	926,954	403,216
Income (loss) before income taxes									1,014,863	836,818	312,402
Depreciation and amortization									227,752	213,227	205,827
Capital expenditures									128,749	160,767	71,752
Assets	4,257,167				4,126,448				4,257,167	4,126,448
Steel Operations | Other segments
Segment Reporting Information
Net sales									243,646	236,213	218,963
Steel Operations | U.S.
Segment Reporting Information
Net sales									6,613,944	5,399,275	4,935,549
Steel Operations | Non-U.S.
Segment Reporting Information
Net sales									317,819	235,436	267,963
Metals Recycling Operations
Segment Reporting Information
Net sales									2,813,004	2,171,877	2,337,716
Operating income (loss)									71,052	20,423	(448,137)
Income (loss) before income taxes									64,638	8,378	(465,426)
Depreciation and amortization									48,830	56,483	65,640
Capital expenditures									25,998	29,443	21,874
Assets	1,011,298				1,038,946				1,011,298	1,038,946
Metals Recycling Operations | Other segments
Segment Reporting Information
Net sales									1,402,963	1,002,536	904,713
Metals Recycling Operations | U.S.
Segment Reporting Information
Net sales									1,204,188	1,007,781	1,249,061
Metals Recycling Operations | Non-U.S.
Segment Reporting Information
Net sales									205,853	161,560	183,942
Steel Fabrication Operations
Segment Reporting Information
Net sales									824,425	703,522	673,399
Operating income (loss)									87,295	90,955	115,947
Income (loss) before income taxes									81,046	82,776	108,795
Depreciation and amortization									11,507	10,952	9,587
Capital expenditures									7,506	3,123	3,395
Assets	384,402				340,902				384,402	340,902
Steel Fabrication Operations | Other segments
Segment Reporting Information
Net sales									644	2,481	25
Steel Fabrication Operations | U.S.
Segment Reporting Information
Net sales									823,630	700,852	671,323
Steel Fabrication Operations | Non-U.S.
Segment Reporting Information
Net sales									151	189	2,051
Other
Segment Reporting Information
Net sales									375,511	276,912	314,847
Operating income (loss)									(190,785)	(301,116)	(148,784)
Income (loss) before income taxes									(226,001)	(354,589)	(202,862)
Depreciation and amortization									10,910	15,652	13,746
Capital expenditures									2,682	4,827	17,480
Assets	1,334,361				1,054,448				1,334,361	1,054,448
Other | Other segments
Segment Reporting Information
Net sales									2,299	4,896	30,325
Other | U.S.
Segment Reporting Information
Net sales									373,212	271,828	283,965
Other | Non-U.S.
Segment Reporting Information
Net sales										188	557
Eliminations
Segment Reporting Information
Net sales									(1,649,552)	(1,246,126)	(1,154,026)
Operating income (loss)									689	(9,250)	4,974
Income (loss) before income taxes									689	(9,250)	4,974
Depreciation and amortization										(205)	(205)
Assets	$ (131,496)				$ (137,012)				(131,496)	(137,012)
Eliminations | Other segments
Segment Reporting Information
Net sales									$ (1,649,552)	$ (1,246,126)	$ (1,154,026)

Transactions with Affiliated 71

Transactions with Affiliated Companies (Schedule of Related Party Transactions) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Sales	$ 174,584	$ 169,929	$ 187,178
Accounts receivable	22,422	26,219
Heidtman [Member]
Related Party Transaction [Line Items]
Sales	$ 150,981	$ 142,624	$ 162,742
Percentage of consolidated net sales	2.00%	2.00%	2.00%
Accounts receivable	$ 19,354	$ 20,737	$ 30,627
Purchases	10,684	9,017	11,429
Accounts payable	663	494	431
Other Smaller Affiliated Entities [Member]
Related Party Transaction [Line Items]
Sales	23,603	27,305	24,436
Accounts receivable	3,068	5,483	3,645
Purchases	219,975	165,091	178,102
Accounts payable	$ 15,020	$ 12,576	$ 6,199

Segment Information - Other Foo

Segment Information - Other Footnote (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating income (loss)
Corporate SG & A									$ (394,631)	$ (374,009)	$ (328,758)
Profit sharing									(91,309)	(71,285)	(23,064)
Asset impairment charges										132,839	428,500
Operating income (loss)	$ 195,947	$ 271,015	$ 265,353	$ 334,566	$ 56,024	$ 283,855	$ 256,122	$ 131,965	1,066,881	727,966	(72,784)
Assets
Cash and equivalents	1,028,649				841,483				1,028,649	841,483	727,032	$ 361,363
Accounts receivable	868,837				729,784				868,837	729,784
Inventories	1,519,347				1,275,211				1,519,347	1,275,211
Property, plant and equipment, net	2,675,904				2,787,215				2,675,904	2,787,215
Other	27,684				29,514				27,684	29,514
Total assets	6,855,732				6,423,732				6,855,732	6,423,732
Minnesota ironmaking operations
Operating income (loss)
Asset impairment charges									127,300	5,500	428,500
Other
Operating income (loss)
Corporate SG & A									(49,400)	(48,900)	(37,800)
Company-wide equity-based compensation									(36,500)	(30,400)	(27,100)
Profit sharing									(87,600)	(66,400)	(17,700)
Other, net									(4,500)	(10,500)	(10,500)
Operating income (loss)									(190,785)	(301,116)	(148,784)
Assets
Cash and equivalents	1,003,200				775,700				1,003,200	775,700
Accounts receivable	9,400				2,000				9,400	2,000
Inventories	58,800				35,400				58,800	35,400
Income tax receivable	57,300				25,300				57,300	25,300
Property, plant and equipment, net	160,900				168,500				160,900	168,500
Intra Company Debt	13,400				12,100				13,400	12,100
Other	31,400				35,400				31,400	35,400
Total assets	1,334,361				1,054,448				1,334,361	1,054,448
Other | Minnesota ironmaking operations
Operating income (loss)
Operating income (loss)									12,800
Other | MINNESOTA | Minnesota ironmaking operations
Operating income (loss)
Asset impairment charges										129,100	(148,800)
Operating income (loss)										(15,800)	(55,700)
Metals Recycling Operations
Operating income (loss)
Operating income (loss)									71,052	20,423	$ (448,137)
Assets
Total assets	$ 1,011,298				$ 1,038,946				$ 1,011,298	$ 1,038,946

Segment Information - Eliminati

Segment Information - Eliminations Footnote (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating income (loss)
Operating income (loss)	$ 195,947	$ 271,015	$ 265,353	$ 334,566	$ 56,024	$ 283,855	$ 256,122	$ 131,965	$ 1,066,881	$ 727,966	$ (72,784)
Gross profit	320,824	$ 396,518	$ 392,518	$ 472,154	309,942	$ 408,503	$ 380,383	$ 236,036	1,582,014	1,334,864	731,718
Asset impairment charges										132,839	428,500
Assets elimination
Accounts receivable	868,837				729,784				868,837	729,784
Other	27,684				29,514				27,684	29,514
Total assets	6,855,732				6,423,732				6,855,732	6,423,732
Eliminations
Operating income (loss)
Operating income (loss)									689	(9,250)	$ 4,974
Gross profit										(11,100)
Asset impairment charges										1,800
Assets elimination
Accounts receivable	(106,100)				(112,300)				(106,100)	(112,300)
Elimination of intra-company debt	(13,400)				(12,100)				(13,400)	(12,100)
Other	(12,000)				12,600				(12,000)	12,600
Total assets	$ (131,496)				$ (137,012)				$ (131,496)	$ (137,012)

Condensed Consolidating Infor74

Condensed Consolidating Information - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Consolidating Balance Sheets
Cash and equivalents	$ 1,028,649	$ 841,483	$ 727,032	$ 361,363
Accounts receivable, net	868,837	729,784
Inventories	1,519,347	1,275,211
Other current assets	91,509	83,197
Total current assets	3,508,342	2,929,675
Property, plant and equipment, net	2,675,904	2,787,215
Intangible assets, net	256,909	283,977
Goodwill	386,893	393,351
Other assets, including investments in subs	27,684	29,514
Total assets	6,855,732	6,423,732
Accounts payable	489,448	395,196
Accrued expenses	350,276	313,987
Current maturities of long-term debt	28,795	3,632
Total current liabilities	868,519	712,815
Long-term debt	2,353,145	2,353,194
Other liabilities	327,760	469,024
Total liabilities	3,549,424	3,535,033
Redeemable noncontrolling interests	111,240	111,240
Common stock	644	641
Treasury stock	(665,297)	(416,829)
Additional paid-in capital	1,141,534	1,132,749
Retained earnings (deficit)	2,874,693	2,210,459
Total Steel Dynamics, Inc. equity	3,351,574	2,927,020
Noncontrolling interests	(156,506)	(149,561)
Total equity	3,195,068	2,777,459	2,545,111	2,795,527
Total liabilities and equity	6,855,732	6,423,732
Parent
Condensed Consolidating Balance Sheets
Cash and equivalents	1,001,405	766,685	636,877	265,313
Accounts receivable, net	274,968	229,148
Inventories	685,103	587,319
Other current assets	73,748	45,049
Total current assets	2,035,224	1,628,201
Property, plant and equipment, net	859,419	899,370
Other assets, including investments in subs	2,512,594	2,769,884
Total assets	5,407,237	5,297,455
Accounts payable	168,282	141,089
Accrued expenses	222,023	198,085
Current maturities of long-term debt	731	674
Total current liabilities	391,036	339,848
Long-term debt	2,326,466	2,324,298
Other liabilities	(661,839)	(293,711)
Total liabilities	2,055,663	2,370,435
Common stock	644	641
Treasury stock	(665,297)	(416,829)
Additional paid-in capital	1,141,534	1,132,749
Retained earnings (deficit)	2,874,693	2,210,459
Total Steel Dynamics, Inc. equity	3,351,574	2,927,020
Total equity	3,351,574	2,927,020
Total liabilities and equity	5,407,237	5,297,455
Guarantors
Condensed Consolidating Balance Sheets
Cash and equivalents	20,441	54,677	81,976	81,690
Accounts receivable, net	1,426,036	1,257,245
Inventories	752,151	639,148
Other current assets	16,005	36,062
Total current assets	2,214,633	1,987,132
Property, plant and equipment, net	1,618,438	1,679,751
Intangible assets, net	225,503	251,919
Goodwill	379,069	385,527
Other assets, including investments in subs	6,622	7,335
Total assets	4,444,265	4,311,664
Accounts payable	316,676	265,764
Accrued expenses	254,196	220,917
Current maturities of long-term debt		700
Total current liabilities	570,872	487,381
Other liabilities	869,196	1,219,444
Total liabilities	1,440,068	1,706,825
Common stock	1,727,859	1,727,859
Additional paid-in capital	128,076	128,076
Retained earnings (deficit)	1,148,262	748,904
Total Steel Dynamics, Inc. equity	3,004,197	2,604,839
Total equity	3,004,197	2,604,839
Total liabilities and equity	4,444,265	4,311,664
Combined Non-Guarantors
Condensed Consolidating Balance Sheets
Cash and equivalents	6,803	20,121	$ 8,179	$ 14,360
Accounts receivable, net	37,387	23,689
Inventories	91,890	58,696
Other current assets	5,962	4,447
Total current assets	142,042	106,953
Property, plant and equipment, net	198,047	208,094
Intangible assets, net	31,406	32,058
Goodwill	7,824	7,824
Other assets, including investments in subs	5,505	5,832
Total assets	384,824	360,761
Accounts payable	101,948	89,659
Accrued expenses	10,243	8,793
Current maturities of long-term debt	56,454	29,347
Total current liabilities	168,645	127,799
Long-term debt	169,799	168,566
Other liabilities	24,868	42,482
Total liabilities	363,312	338,847
Redeemable noncontrolling interests	111,240	111,240
Common stock	14,908	14,908
Additional paid-in capital	797,196	779,678
Retained earnings (deficit)	(745,326)	(734,351)
Total Steel Dynamics, Inc. equity	66,778	60,235
Noncontrolling interests	(156,506)	(149,561)
Total equity	(89,728)	(89,326)
Total liabilities and equity	384,824	360,761
Consolidating Adjustments
Condensed Consolidating Balance Sheets
Accounts receivable, net	(869,554)	(780,298)
Inventories	(9,797)	(9,952)
Other current assets	(4,206)	(2,361)
Total current assets	(883,557)	(792,611)
Other assets, including investments in subs	(2,497,037)	(2,753,537)
Total assets	(3,380,594)	(3,546,148)
Accounts payable	(97,458)	(101,316)
Accrued expenses	(136,186)	(113,808)
Current maturities of long-term debt	(28,390)	(27,089)
Total current liabilities	(262,034)	(242,213)
Long-term debt	(143,120)	(139,670)
Other liabilities	95,535	(499,191)
Total liabilities	(309,619)	(881,074)
Common stock	(1,742,767)	(1,742,767)
Additional paid-in capital	(925,272)	(907,754)
Retained earnings (deficit)	(402,936)	(14,553)
Total Steel Dynamics, Inc. equity	(3,070,975)	(2,665,074)
Total equity	(3,070,975)	(2,665,074)
Total liabilities and equity	$ (3,380,594)	$ (3,546,148)

Commitments and Contingencies75

Commitments and Contingencies (Schedule of Unconditional Purchase Obligations) (Details) - Inventories [Member] $ in Thousands	Dec. 31, 2017USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
2,017	$ 312,736
2,018	116,779
2,019	104,300
2,020	90,894
2,021	83,696
Thereafter	75,337
Unrecorded Unconditional Purchase Obligation, Total	$ 783,742

Condensed Consolidating Infor76

Condensed Consolidating Information - Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Consolidating Statements of Operations
Net sales	$ 2,336,479	$ 2,443,382	$ 2,390,720	$ 2,368,216	$ 1,910,596	$ 2,101,310	$ 2,023,902	$ 1,741,301	$ 9,538,797	$ 7,777,109	$ 7,594,411
Costs of goods sold									7,956,783	6,442,245	6,862,693
Gross profit	320,824	396,518	392,518	472,154	309,942	408,503	380,383	236,036	1,582,014	1,334,864	731,718
Selling, general and administrative									515,133	474,059	376,002
Asset impairment charges										132,839	428,500
Operating income	195,947	271,015	265,353	334,566	56,024	283,855	256,122	131,965	1,066,881	727,966	(72,784)
Interest expense, net of capitalized interest									134,399	146,037	153,950
Other (income) expense, net									(2,753)	17,796	15,383
Income before income taxes									935,235	564,133	(242,117)
Income taxes (benefit)									129,439	204,127	(96,947)
Net income	303,171	151,012	152,947	198,666	3,832	154,413	140,443	61,318	805,796	360,006	(145,170)
Net loss attributable to noncontrolling interests									6,945	22,109	14,859
Net income attributable to Steel Dynamics, Inc.	$ 304,733	$ 153,258	$ 153,933	$ 200,817	$ 20,012	$ 157,397	$ 141,969	$ 62,737	812,741	382,115	(130,311)
Parent
Condensed Consolidating Statements of Operations
Net sales									3,702,597	3,037,801	2,908,904
Costs of goods sold									2,994,257	2,428,863	2,515,621
Gross profit									708,340	608,938	393,283
Selling, general and administrative									221,736	196,442	128,929
Asset impairment charges										12,700
Operating income									486,604	399,796	264,354
Interest expense, net of capitalized interest									73,521	71,182	75,457
Other (income) expense, net									(2,305)	14,200	13,970
Income before income taxes									415,388	314,414	174,927
Income taxes (benefit)									(69,961)	69,454	(124,626)
Net income									485,349	244,960	299,553
Equity in net income of subsidiaries									327,392	137,155	(429,864)
Net income attributable to Steel Dynamics, Inc.									812,741	382,115	(130,311)
Guarantors
Condensed Consolidating Statements of Operations
Net sales									10,366,526	8,356,727	8,132,043
Costs of goods sold									9,399,996	7,522,791	7,646,411
Gross profit									966,530	833,936	485,632
Selling, general and administrative									293,161	281,071	254,106
Asset impairment charges										5,500	428,500
Operating income									673,369	547,365	(196,974)
Interest expense, net of capitalized interest									57,622	72,420	76,009
Other (income) expense, net									(9,937)	(5,363)	332
Income before income taxes									625,684	480,308	(273,315)
Income taxes (benefit)									226,327	180,990	61,571
Net income									399,357	299,318	(334,886)
Net income attributable to Steel Dynamics, Inc.									399,357	299,318	(334,886)
Combined Non-Guarantors
Condensed Consolidating Statements of Operations
Net sales									597,789	388,071	361,944
Costs of goods sold									577,205	390,313	420,281
Gross profit									20,584	(2,242)	(58,337)
Selling, general and administrative									20,493	16,103	11,893
Asset impairment charges										116,445
Operating income									91	(134,790)	(70,230)
Interest expense, net of capitalized interest									12,901	10,874	6,969
Other (income) expense, net									(156)	520	(3,404)
Income before income taxes									(12,654)	(146,184)	(73,795)
Income taxes (benefit)									5,266	(15,825)	(4,627)
Net income									(17,920)	(130,359)	(69,168)
Net loss attributable to noncontrolling interests									6,945	22,109	14,859
Net income attributable to Steel Dynamics, Inc.									(10,975)	(108,250)	(54,309)
Consolidating Adjustments
Condensed Consolidating Statements of Operations
Net sales									(5,128,115)	(4,005,490)	(3,808,480)
Costs of goods sold									(5,014,675)	(3,899,722)	(3,719,620)
Gross profit									(113,440)	(105,768)	(88,860)
Selling, general and administrative									(20,257)	(19,557)	(18,926)
Asset impairment charges										(1,806)
Operating income									(93,183)	(84,405)	(69,934)
Interest expense, net of capitalized interest									(9,645)	(8,439)	(4,485)
Other (income) expense, net									9,645	8,439	4,485
Income before income taxes									(93,183)	(84,405)	(69,934)
Income taxes (benefit)									(32,193)	(30,492)	(29,265)
Net income									(60,990)	(53,913)	(40,669)
Equity in net income of subsidiaries									(327,392)	(137,155)	429,864
Net income attributable to Steel Dynamics, Inc.									$ (388,382)	$ (191,068)	$ 389,195

Condensed Consolidating Infor77

Condensed Consolidating Information - Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Consolidating Statements of Cash Flows
Net cash provided by (used in) operating activities	$ 739,606	$ 852,769	$ 1,053,625
Net cash used in investing activities	(139,105)	(312,893)	(142,627)
Net cash provided by (used in) financing activities	(413,335)	(425,425)	(545,329)
Increase in cash and equivalents	187,166	114,451	365,669
Cash and equivalents at beginning of period	841,483	727,032	361,363
Cash and equivalents at end of period	1,028,649	841,483	727,032
Parent
Condensed Consolidating Statements of Cash Flows
Net cash provided by (used in) operating activities	171,300	326,216	436,012
Net cash used in investing activities	(62,534)	(161,043)	(64,457)
Net cash provided by (used in) financing activities	125,954	(35,365)	9
Increase in cash and equivalents	234,720	129,808	371,564
Cash and equivalents at beginning of period	766,685	636,877	265,313
Cash and equivalents at end of period	1,001,405	766,685	636,877
Guarantors
Condensed Consolidating Statements of Cash Flows
Net cash provided by (used in) operating activities	594,279	517,699	594,437
Net cash used in investing activities	(73,021)	(140,027)	(82,751)
Net cash provided by (used in) financing activities	(555,494)	(404,971)	(511,400)
Increase in cash and equivalents	(34,236)	(27,299)	286
Cash and equivalents at beginning of period	54,677	81,976	81,690
Cash and equivalents at end of period	20,441	54,677	81,976
Combined Non-Guarantors
Condensed Consolidating Statements of Cash Flows
Net cash provided by (used in) operating activities	(31,719)	6,057	19,388
Net cash used in investing activities	(8,301)	(9,578)	(15,703)
Net cash provided by (used in) financing activities	26,702	15,463	(9,866)
Increase in cash and equivalents	(13,318)	11,942	(6,181)
Cash and equivalents at beginning of period	20,121	8,179	14,360
Cash and equivalents at end of period	6,803	20,121	8,179
Consolidating Adjustments
Condensed Consolidating Statements of Cash Flows
Net cash provided by (used in) operating activities	5,746	2,797	3,788
Net cash used in investing activities	4,751	(2,245)	20,284
Net cash provided by (used in) financing activities	$ (10,497)	$ (552)	$ (24,072)

Quarterly Financial Informati78

Quarterly Financial Information (Details) - USD ($)	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net sales		$ 2,336,479,000	$ 2,443,382,000	$ 2,390,720,000	$ 2,368,216,000	$ 1,910,596,000	$ 2,101,310,000	$ 2,023,902,000	$ 1,741,301,000	$ 9,538,797,000	$ 7,777,109,000	$ 7,594,411,000
Gross profit		320,824,000	396,518,000	392,518,000	472,154,000	309,942,000	408,503,000	380,383,000	236,036,000	1,582,014,000	1,334,864,000	731,718,000
Operating income (loss)		195,947,000	271,015,000	265,353,000	334,566,000	56,024,000	283,855,000	256,122,000	131,965,000	1,066,881,000	727,966,000	(72,784,000)
Net income (loss)		303,171,000	151,012,000	152,947,000	198,666,000	3,832,000	154,413,000	140,443,000	61,318,000	805,796,000	360,006,000	(145,170,000)
Net income (loss) attributable to Steel Dynamics, Inc.		$ 304,733,000	$ 153,258,000	$ 153,933,000	$ 200,817,000	$ 20,012,000	$ 157,397,000	$ 141,969,000	$ 62,737,000	$ 812,741,000	382,115,000	(130,311,000)
Impairment charges											$ 132,839,000	$ 428,500,000
Earnings (loss) per share:
Basic (in dollars per share)		$ 1.28	$ 0.64	$ 0.64	$ 0.83	$ 0.08	$ 0.65	$ 0.58	$ 0.26	$ 3.38	$ 1.57	$ (0.54)
Diluted (in dollars per share)		$ 1.28	$ 0.64	$ 0.63	$ 0.82	$ 0.08	$ 0.64	$ 0.58	$ 0.26	$ 3.36	$ 1.56	$ (0.54)
Long Term Debt
Call and repayment of debt										$ 609,914,000	$ 728,993,000	$ 625,924,000
Income Tax Expense (Benefit) Due to Tax Reform		$ 180,600,000								(180,600,000)
6 1/8% senior notes, due 2019
Long Term Debt
Call premiums and write off of deferred financing costs						$ 16,500,000
Call and repayment of debt	$ 266,300,000
Debt Instrument, Face Amount		$ 400,000,000								$ 400,000,000
Stated interest rate		6.125%								6.125%
Senior Notes 5.000 Percent Due 2026 [Member]
Long Term Debt
Debt Instrument, Face Amount		$ 400,000,000								$ 400,000,000
Stated interest rate		5.00%								5.00%
7 5/8% senior notes, due 2020
Long Term Debt
Call and repayment of debt											350,000,000,000
Stated interest rate												7.625%
Senior term loan
Long Term Debt
Call and repayment of debt	$ 228,100,000					228,100,000
Metals Recycling Operations
Net sales										$ 2,813,004,000	2,171,877,000	$ 2,337,716,000
Operating income (loss)										71,052,000	20,423,000	(448,137,000)
Parent
Net sales										3,702,597,000	3,037,801,000	2,908,904,000
Gross profit										708,340,000	608,938,000	393,283,000
Operating income (loss)										486,604,000	399,796,000	264,354,000
Net income (loss)										485,349,000	244,960,000	299,553,000
Net income (loss) attributable to Steel Dynamics, Inc.										812,741,000	382,115,000	(130,311,000)
Impairment charges											12,700,000
Minnesota ironmaking operations
Impairment charges										127,300,000	$ 5,500,000	$ 428,500,000
Operating Income (Loss) [Member] | Minnesota ironmaking operations
Impairment charges						132,800,000
Net Income (Loss) [Member] | Minnesota ironmaking operations
Impairment charges						89,500,000
Net Income (Loss) Attributable to Parent [Member] | Minnesota ironmaking operations
Impairment charges						$ 76,400,000
Noncontrolling Interests | Minnesota ironmaking operations
Impairment charges										$ 13,100,000