Nucor (NUE) 10-K 28 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Feb. 22, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	NUE
Entity Registrant Name	NUCOR CORP
Entity Central Index Key	73,309
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		305,381,583
Entity Public Float			$ 19,670

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents (Note 14)	$ 1,398,886	$ 949,104
Short-term investments (Notes 4 and 14)	0	50,000
Accounts receivable, net (Note 5)	2,505,568	2,028,545
Inventories, net (Note 6)	4,553,500	3,461,686
Other current assets (Notes 13 and 19)	178,311	335,085
Total current assets	8,636,265	6,824,420
Property, plant and equipment, net (Note 7)	5,334,748	5,093,147
Goodwill (Notes 3 and 8)	2,184,336	2,196,058
Other intangible assets, net (Notes 3 and 8)	828,504	914,646
Other assets (Note 9)	936,735	812,987
Total assets	17,920,588	15,841,258
Current liabilities:
Short-term debt (Notes 11 and 14)	57,870	52,833
Long-term debt due within one year (Notes 11 and 14)		500,000
Accounts payable (Note 10)	1,428,191	1,181,346
Salaries, wages and related accruals (Note 17)	709,397	516,660
Accrued expenses and other current liabilities (Notes 10, 13 and 15)	610,842	573,925
Total current liabilities	2,806,300	2,824,764
Long-term debt due after one year (Notes 11 and 14)	4,233,276	3,242,242
Deferred credits and other liabilities (Notes 13, 15, 17 and 19)	679,044	689,464
Total liabilities	7,718,620	6,756,470
Commitments and contingencies (Notes 13 and 15)
Nucor stockholders' equity (Notes 12 and 16):
Common stock (800,000 shares authorized; 380,154 and 379,900 shares issued, respectively)	152,061	151,960
Additional paid-in capital	2,073,715	2,021,339
Retained earnings	10,337,445	8,463,709
Accumulated other comprehensive loss, net of income taxes (Notes 13 and 20)	(304,133)	(254,681)
Treasury stock (74,562 and 61,931 shares, respectively)	(2,467,010)	(1,643,291)
Total Nucor stockholders' equity	9,792,078	8,739,036
Noncontrolling interests	409,890	345,752
Total equity	10,201,968	9,084,788
Total liabilities and equity	$ 17,920,588	$ 15,841,258

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock shares authorized	800,000,000	800,000,000
Common stock shares issued	380,154,000	379,900,000
Treasury stock	74,562,000	61,931,000

Consolidated Statements of Earn

Consolidated Statements of Earnings - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales (Notes 23 and 24)	$ 25,067,279	$ 20,252,393	$ 16,208,122
Costs, expenses and other:
Cost of products sold (Notes 13 and 20)	20,771,871	17,682,986	14,182,215
Marketing, administrative and other expenses	860,722	687,531	596,761
Equity in earnings of unconsolidated subsidiaries	(40,240)	(41,661)	(38,757)
Impairment of assets (Notes 7 and 24)	110,000
Interest expense, net (Notes 18 and 19)	135,535	173,580	169,244
Costs, expenses and other, total	21,837,888	18,502,436	14,909,463
Earnings before income taxes and noncontrolling interests	3,229,391	1,749,957	1,298,659
Provision for income taxes (Notes 19 and 24)	748,307	369,386	398,243
Net earnings	2,481,084	1,380,571	900,416
Earnings attributable to noncontrolling interests	120,317	61,883	104,145
Net earnings attributable to Nucor stockholders	$ 2,360,767	$ 1,318,688	$ 796,271
Net earnings per share (Note 21):
Basic	$ 7.44	$ 4.11	$ 2.48
Diluted	$ 7.42	$ 4.10	$ 2.48

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Comprehensive Income [Abstract]
Net earnings	$ 2,481,084	$ 1,380,571	$ 900,416
Other comprehensive income (loss):
Net unrealized (loss) income on hedging derivatives, net of income taxes of ($300), ($2,600) and $1,500 for 2018, 2017 and 2016, respectively	(3,568)	(4,523)	2,570
Reclassification adjustment for (gain) loss on settlement of hedging derivatives included in net earnings, net of income taxes of $0, $400 and $5,800 for 2018, 2017 and 2016, respectively	(132)	973	9,880
Foreign currency translation (loss) gain, net of income taxes of $0 for 2018, 2017 and 2016	(47,133)	68,657	25,495
Adjustment to early retiree medical plan, net of income taxes of $514, ($767) and ($1,291) for 2018, 2017 and 2016, respectively	1,731	(1,530)	(3,589)
Reclassification adjustment for gain on early retiree medical plan included in net earnings, net of income taxes of ($108), ($279) and ($309) for 2018, 2017 and 2016, respectively	(350)	(415)	(837)
Net current-period other comprehensive income (loss)	(49,452)	63,162	33,519
Comprehensive income	2,431,632	1,443,733	933,935
Comprehensive income attributable to noncontrolling interests	(120,317)	(61,883)	(104,145)
Comprehensive income attributable to Nucor stockholders	$ 2,311,315	$ 1,381,850	$ 829,790

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Comprehensive Income [Abstract]
Net unrealized (loss) income on hedging derivatives, tax	$ (300)	$ (2,600)	$ 1,500
Reclassification adjustment for (gain) loss on settlement of hedging derivatives included in net earnings, tax effect	0	400	5,800
Foreign currency translation (loss) gain tax	0	0	0
Adjustment to early retiree medical plan, tax effect	514	(767)	(1,291)
Reclassification adjustment for gain on early retiree medical plan included in net earnings, tax effect	$ (108)	$ (279)	$ (309)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) [Member]	Treasury Stock (at cost) [Member]	Total Nucor Stockholders' Equity [Member]	Noncontrolling Interests [Member]
BALANCES, beginning of period at Dec. 31, 2015	$ 7,849,877	$ 151,426	$ 1,918,970	$ 7,316,910	$ (351,362)	$ (1,558,128)	$ 7,477,816	$ 372,061
BALANCES, shares at beginning of period at Dec. 31, 2015		378,566				60,604
Net earnings	900,416			796,271			796,271	104,145
Other comprehensive income (loss)	33,519				33,519		33,519
Stock options exercised	$ 15,670	$ 160	15,510				15,670
Stock options exercised (in shares)	400	400
Stock option expense	$ 7,833		7,833				7,833
Issuance of stock under award plans, net of forfeitures	35,953	$ 148	32,118			$ 3,687	35,953
Issuance of stock under award plans, net of forfeitures, shares		368				(143)
Amortization of unearned compensation	843		843				843
Treasury stock value acquired	(5,173)					$ (5,173)	(5,173)
Treasury stock shares acquired						136
Cash dividends declared	(482,265)			(482,265)			(482,265)
Distributions to noncontrolling interests	(99,588)							(99,588)
Other	(2,377)		(602)				(602)	(1,775)
BALANCES, end of period at Dec. 31, 2016	8,254,708	$ 151,734	1,974,672	7,630,916	(317,843)	$ (1,559,614)	7,879,865	374,843
BALANCES, shares at end of period at Dec. 31, 2016		379,334				60,597
Net earnings	1,380,571			1,318,688			1,318,688	61,883
Other comprehensive income (loss)	63,162				63,162		63,162
Stock options exercised	$ 7,069	$ 73	6,996				7,069
Stock options exercised (in shares)	183	183
Stock option expense	$ 8,233		8,233				8,233
Issuance of stock under award plans, net of forfeitures	37,018	$ 153	30,238			$ 6,627	37,018
Issuance of stock under award plans, net of forfeitures, shares		383				(257)
Amortization of unearned compensation	1,200		1,200				1,200
Treasury stock value acquired	(90,304)					$ (90,304)	(90,304)
Treasury stock shares acquired						1,591
Cash dividends declared	(485,895)			(485,895)			(485,895)
Distributions to noncontrolling interests	(90,974)							(90,974)
BALANCES, end of period at Dec. 31, 2017	9,084,788	$ 151,960	2,021,339	8,463,709	(254,681)	$ (1,643,291)	8,739,036	345,752
BALANCES, shares at end of period at Dec. 31, 2017		379,900				61,931
Net earnings	2,481,084			2,360,767			2,360,767	120,317
Other comprehensive income (loss)	(49,452)				(49,452)		(49,452)
Stock options exercised	$ 24,102	$ 84	14,675			$ 9,343	24,102
Stock options exercised (in shares)	543	210				(333)
Stock option expense	$ 4,563		4,563				4,563
Issuance of stock under award plans, net of forfeitures	52,313	$ 17	31,361			$ 20,935	52,313
Issuance of stock under award plans, net of forfeitures, shares		44				(762)
Amortization of unearned compensation	1,777		1,777				1,777
Treasury stock value acquired	(853,997)					$ (853,997)	(853,997)
Treasury stock shares acquired						13,726
Cash dividends declared	(487,031)			(487,031)			(487,031)
Distributions to noncontrolling interests	(56,179)							(56,179)
BALANCES, end of period at Dec. 31, 2018	$ 10,201,968	$ 152,061	$ 2,073,715	$ 10,337,445	$ (304,133)	$ (2,467,010)	$ 9,792,078	$ 409,890
BALANCES, shares at end of period at Dec. 31, 2018		380,154				74,562

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Cash dividends declared per share	$ 1.5400	$ 1.5125	$ 1.5025

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net earnings	$ 2,481,084	$ 1,380,571	$ 900,416
Adjustments:
Depreciation	630,879	635,833	613,192
Amortization	88,758	91,228	73,862
Stock-based compensation	73,422	64,176	56,511
Deferred income taxes	3,017	(221,173)	71,455
Distributions from affiliates	30,196	49,295	40,602
Equity in earnings of unconsolidated affiliates	(40,240)	(41,661)	(38,757)
Impairment of assets	110,000
Changes in assets and liabilities (exclusive of acquisitions and dispositions):
Accounts receivable	(485,433)	(329,501)	(217,736)
Inventories	(1,092,101)	(900,946)	(132,639)
Accounts payable	235,572	314,817	236,788
Federal income taxes	163,743	(107,577)	3,555
Salaries, wages and related accruals	204,796	87,700	133,625
Other operating activities	(9,741)	32,576	9,127
Cash provided by operating activities	2,393,952	1,055,338	1,750,001
Investing activities:
Capital expenditures	(982,531)	(448,555)	(604,840)
Investment in and advances to affiliates	(121,412)	(59,000)	(63,167)
Divestiture of affiliates			135,000
Disposition of plant and equipment	31,589	25,315	18,571
Acquisitions (net of cash acquired)	(33,063)	(544,041)	(474,788)
Purchases of investments		(50,000)	(650,000)
Proceeds from the sale of investments	50,000	150,000	600,000
Other investing activities	25,348	7,389	14,106
Cash used in investing activities	(1,030,069)	(918,892)	(1,025,118)
Financing activities:
Net change in short-term debt	5,037	34,872	(33,360)
Proceeds from long-term debt, net of discount	995,710
Repayment of long-term debt	(500,000)	(600,000)
Bond issuance related costs	(7,625)
Issuance of common stock	24,101	7,070	15,670
Payment of tax withholdings on certain stock-based compensation	(22,123)	(14,408)	(12,387)
Excess tax benefits from stock-based compensation			2,784
Distributions to noncontrolling interests	(56,179)	(90,974)	(99,588)
Cash dividends	(485,376)	(485,321)	(481,083)
Acquisition of treasury stock	(853,997)	(90,304)	(5,173)
Other financing activities	(7,725)	(3,241)	(13,297)
Cash used in financing activities	(908,177)	(1,242,306)	(626,434)
Effect of exchange rate changes on cash	(5,924)	9,003	8,043
Increase (decrease) in cash and cash equivalents	449,782	(1,096,857)	106,492
Cash and cash equivalents - beginning of year	949,104	2,045,961	1,939,469
Cash and cash equivalents - end of year	1,398,886	949,104	2,045,961
Non-cash investing activity:
Change in accrued plant and equipment purchases and assets recorded under capital lease arrangements	$ 14,725	$ 58,519	$ 12,837

Nature of Operations and Basis

Nature of Operations and Basis of Presentation	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations and Basis of Presentation	1. Nature of Operations and Basis of Presentation Nature of Operations Nucor is principally a manufacturer of steel and steel products, as well as a scrap broker and processor, with operating facilities and customers primarily located in North America. Principles of Consolidation The consolidated financial statements include Nucor and its controlled subsidiaries, including Nucor-Yamato Steel Company, a limited partnership of which Nucor owns 51%. All intercompany transactions are eliminated. Distributions are made to noncontrolling interest partners in Nucor-Yamato Steel Company in accordance with the limited partnership agreement by mutual agreement of the general partners. At a minimum, sufficient cash is distributed so that each partner may pay its U.S. federal and state income taxes. Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles in the United States of America requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from these estimates. Reclassifications In the first quarter of 2018, the Company began reporting its tubular products and piling products businesses as part of the steel products segment. These businesses were previously included in the steel mills segment and were reclassified to the steel products segment as part of a realignment of Nucor’s reportable segments to reflect the way in which they are now viewed by management and how segment performance assessments began to be made by the chief operating decision maker beginning in such period. As a result, certain prior period amounts have been reclassified to conform to the current year presentation. These reclassifications did not have an impact on the consolidated financial statements of the Company for the prior periods presented. See Note 22 for more information related to this segment realignment.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Cash and Cash Equivalents Cash equivalents are recorded at cost plus accrued interest, which approximates fair value, and have original maturities of three months or less at the date of purchase. Cash and cash equivalents are maintained primarily with a few high-credit quality financial institutions. Short-term Investments Short-term investments are recorded at cost plus accrued interest, which approximates fair value. Unrealized gains and losses on investments classified as available-for-sale re-evaluates Inventories Inventories are stated at the lower of cost or market. The Company records any amount required to reduce the carrying value of inventory to net realizable value as a charge to cost of products sold. Scrap and scrap substitute costs are a very significant component of the raw material, semi-finished and finished product inventory balances. The vast majority of the Company’s inventory is recorded on the first-in, first-out Property, Plant and Equipment Property, plant and equipment is stated at cost, except for property, plant and equipment acquired through acquisitions which is recorded at acquisition date fair value. With the exception of our natural gas wells, depreciation is provided on a straight-line basis over the estimated useful lives of the assets. Depletion of all capitalized costs associated with our natural gas producing properties is expensed on a unit-of-production Goodwill and Other Intangibles Goodwill is the excess of cost over the fair value of net assets of businesses acquired. Goodwill is not amortized but is tested annually for impairment and whenever events or circumstances change that would make it more likely than not that an impairment may have occurred. We perform our annual impairment analysis as of the first day of the fourth quarter each year. The evaluation of impairment involves comparing the current estimated fair value of each reporting unit, which is a level below the reportable segment, to the recorded value, including goodwill. When appropriate, Nucor performs a qualitative assessment to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. For certain reporting units, it is necessary to perform a quantitative analysis. In these instances, a discounted cash flow model is used to determine the current estimated fair value of these reporting units. A number of significant assumptions and estimates are involved in the application of the discounted cash flow model to forecast operating cash flows, which could include market growth and market share, sales volumes and prices, costs to produce, discount rate and estimated capital needs. Management considers historical experience and all available information at the time the fair values of its reporting units are estimated. Assumptions in estimating future cash flows are subject to a high degree of judgment and complexity. Changes in assumptions and estimates may affect the fair value of goodwill and could result in impairment charges in future periods. Finite-lived intangible assets are amortized over their estimated useful lives on a straight-line or accelerated basis. Long-Lived Asset Impairments We evaluate our property, plant and equipment and finite-lived intangible assets for potential impairment on an individual asset basis or at the lowest level asset grouping for which independent cash flows can be separately identified. Asset impairments are assessed whenever circumstances indicate that the carrying amounts of those productive assets could exceed their projected undiscounted cash flows. When it is determined that impairment exists, the related assets are written down to their estimated fair market value. Equity Method Investments Investments in joint ventures in which Nucor shares control over the financial and operating decisions but in which Nucor is not the primary beneficiary are accounted for under the equity method. Each of the Company’s equity method investments is subject to a review for impairment if, and when, circumstances indicate that a decline in value below its carrying amount may have occurred. Examples of such circumstances include, but are not limited to, a significant deterioration in the earnings performance or business prospects of the investee; missed financial projections; a significant adverse change in the regulatory, economic or technological environment of the investee; a significant adverse change in the general market condition of either the geographic area or the industry in which the investee operates; and recurring negative cash flows from operations. When management considers the decline to be other than temporary, the related investment is written down to its estimated fair market value. Derivative Financial Instruments Nucor periodically uses derivative financial instruments primarily to partially manage its exposure to price risk related to natural gas purchases used in the production process as well as its exposure to scrap, copper and aluminum purchased for resale to its customers. In addition, Nucor periodically uses derivatives to partially manage its exposure to changes in interest rates on outstanding debt instruments and uses forward foreign exchange contracts to hedge cash flows associated with certain assets and liabilities, firm commitments and anticipated transactions. Nucor recognizes all derivative instruments in the consolidated balance sheets at fair value. Amounts included in accumulated other comprehensive income (loss) related to cash flow hedges are reclassified into earnings when the underlying transaction is recognized in net earnings. Changes in fair value hedges are reported in earnings along with changes in the fair value of the hedged items. When cash flow and fair value hedges affect net earnings, they are included on the same financial statement line as the underlying transaction (cost of products sold or interest expense). If these instruments do not meet hedge accounting criteria, the change in fair value (or a portion thereof) is recognized immediately in earnings in the same financial statement line as the underlying transaction. Revenue Recognition Nucor recognizes revenue when obligations under the terms of contracts with our customers are satisfied; generally, this occurs upon shipment or when control is transferred. Revenue is measured as the amount of consideration expected to be received in exchange for transferring the goods. In addition, revenue is deferred when cash payments are received or due in advance of performance. See Note 23 for further information. Income Taxes Nucor utilizes the liability method of accounting for income taxes. Under the liability method, deferred taxes are determined based on the temporary differences between the financial statement and tax basis of assets and liabilities using tax rates expected to be in effect during the years in which the basis differences reverse. A valuation allowance is recorded when it is more likely than not that some of the deferred tax assets will not be realized. Nucor recognizes the effect of income tax positions only if those positions are more likely than not of being sustained. Potential accrued interest and penalties related to unrecognized tax benefits are recognized as a component of interest expense and other expenses. The staff of the U.S. Securities and Exchange Commission issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of Accounting Standards Codification 740, Income Taxes, in situations when a registrant does not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Reform Act. Reflected in our 2017 financial results, and in accordance with SAB 118, were certain provisional income tax effects of the Tax Reform Act. Adjustments, as allowed for under SAB 118, to these provisional amounts were made in 2018. The accounting for the Tax Reform Act was completed in the fourth quarter of 2018. Further information on the tax impacts of the Tax Reform Act is included in Note 19 of the Company’s consolidated financial statements. Stock-Based Compensation The Company recognizes the cost of stock-based compensation as an expense using fair value measurement methods. The assumptions used to calculate the fair value of stock-based compensation granted are evaluated and revised for new grants, as necessary, to reflect market conditions and experience. Foreign Currency Translation For Nucor’s operations where the functional currency is other than the U.S. dollar, assets and liabilities have been translated at year-end Recently Adopted Accounting Pronouncements In the first quarter of 2018, Nucor adopted new accounting guidance related to revenue recognition for all contracts using the modified retrospective method. The modified retrospective method requires that the cumulative effect of initially applying this new guidance be recorded as an adjustment to the opening balance of retained earnings in the consolidated balance sheet. The adoption of this new accounting guidance did not have an impact on any prior period earnings attributable to Nucor stockholders, and no adjustment was recorded to the opening retained earnings balance as of January 1, 2018. Retrospective adjustment of comparative prior period information is not required when using the modified retrospective adoption method, and no comparative prior periods have been adjusted for the new guidance. The adoption of the new revenue accounting guidance did not significantly change the way we recognize revenue. To illustrate this, if we had continued using the previous accounting guidance in effect before the adoption of the new revenue accounting guidance, our consolidated net sales for 2018 would have increased approximately $81.4 million, or 0.3%, and cost of products sold would have increased by the same amount. There would have been no impact on any other financial statement line items in the consolidated financial statements for 2018. See Note 23 for disclosures required by the new revenue accounting guidance. In the first quarter of 2018, Nucor adopted new accounting guidance regarding the recognition and measurement of financial assets and financial liabilities. Changes to the current accounting guidance primarily affect the accounting for equity investments, financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. In addition, the Financial Accounting Standards Board clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale In the first quarter of 2018, Nucor adopted new accounting guidance regarding the presentation and classification of certain cash receipts and cash payments in the statement of cash flows. The new guidance addresses specific cash flow presentation issues in order to reduce diversity in existing practice. The adoption of this new guidance did not have a material impact on the Company’s consolidated financial statements. In the first quarter of 2018, Nucor adopted new accounting guidance regarding intra-entity transfers of assets other than inventory. The new guidance requires that an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The adoption of this new guidance did not have a material impact on the Company’s consolidated financial statements. Recently Issued Accounting Pronouncements In February 2016, new accounting guidance was issued regarding the accounting for leases. The new guidance requires all lessees to recognize on the balance sheet right to use assets and lease liabilities for the rights and obligations created by lease arrangements with terms greater than 12 months. The new guidance is effective for the Company for annual and interim reporting periods beginning after December 15, 2018. In July 2018, this accounting guidance was amended to permit companies to recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption and to continue reporting comparative periods prior to adoption in accordance with current lease guidance. The Company will adopt this new guidance in the first quarter of 2019 and will record a cumulative adjustment to the January 1, 2019 retained earnings balance. While the adoption of this new guidance is expected to increase assets and liabilities due to the recognition of lease rights and obligations on the Company’s consolidated balance sheet effective January 1, 2019, the Company does not expect the adoption of this new guidance to have a significant impact on its consolidated financial statements. In February 2018, new accounting guidance was issued regarding the tax effects of the Tax Reform Act. The new guidance allows for a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Reform Act to improve the usefulness of information reported to financial statement users. The new guidance is effective for the Company for annual and interim reporting periods beginning after December 15, 2018. The Company does not expect the adoption of this new guidance to have a material impact on its consolidated financial statements.

Acquisitions and Dispositions

Acquisitions and Dispositions	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Acquisitions and Dispositions	3. Acquisitions and Dispositions On January 20, 2017, Nucor used cash on hand to acquire Republic Conduit (“Republic”) for a purchase price of $331.6 million. Republic produces steel electrical conduit primarily used to protect and route electrical wiring in various nonresidential structures such as hospitals, office buildings and stadiums. With its two facilities located in Kentucky and Georgia, Republic had shipments of approximately 140,000 tons in 2017. This acquisition not only further expands Nucor’s product portfolio to include steel electrical conduit and it is an important, value-added channel to market for Nucor’s sheet mills. Republic’s financial results are included as part of the steel products segment (see Note 22). We have allocated the purchase price for Republic to its individual assets acquired and liabilities assumed. The following table summarizes the fair values of the assets acquired and liabilities assumed of Republic as of the date of acquisition (in thousands): Cash $ 206 Accounts receivable 39,177 Inventory 33,561 Other current assets 1,101 Property, plant and equipment 67,412 Goodwill 115,562 Other intangible assets 89,200 Other assets 3,118 Total assets acquired 349,337 Current liabilities 17,743 Total liabilities assumed 17,743 Net assets acquired $ 331,594 The following table summarizes the purchase price allocation to the identifiable intangible assets of Republic as of the date of acquisition (in thousands, except years): Weighted - Customer relationships $ 80,800 12 years Trademarks and trade names 8,400 13 years $ 89,200 The goodwill of approximately $115.6 million is primarily attributed to the synergies expected to arise after the acquisition. The goodwill is calculated as the excess of the purchase price over the fair values of the assets acquired and liabilities assumed and has been allocated to the steel products segment (see Note 8). Goodwill recognized for tax purposes was $118.6 million, all of which is deductible for such purposes. On October 31, 2016, Nucor used cash on hand to acquire Independence Tube Corporation (“ITC”) for a purchase price of $430.1 million. ITC is a leading manufacturer of hollow structural section (“HSS”) steel tubing, which is primarily used in nonresidential construction markets. ITC has the ability to produce approximately 860,000 tons of HSS steel tubing annually at its four facilities, two of which are in Illinois and the other two are in Alabama. This acquisition not only further expands Nucor’s product portfolio to include the HSS steel tubing market but the Company also believes it is an important, value-added channel to market for Nucor’s hot-rolled We have allocated the purchase price for ITC to its individual assets acquired and liabilities assumed. The following table summarizes the fair values of the assets acquired and liabilities assumed of ITC as of the date of acquisition (in thousands): Cash $ 1,058 Accounts receivable 33,173 Inventory 94,400 Other current assets 1,743 Property, plant and equipment 177,668 Goodwill 29,522 Other intangible assets 130,900 Other assets 1,287 Total assets acquired 469,751 Current liabilities 39,633 Total liabilities assumed 39,633 Net assets acquired $ 430,118 The following table summarizes the purchase price allocation to the identifiable intangible assets of ITC as of the date of acquisition (in thousands, except years): Weighted - Customer relationships $ 119,000 15 years Trademarks and trade names 7,100 15 years Other 4,800 5 years $ 130,900 The goodwill of approximately $29.5 million is primarily attributed to the synergies expected to arise after the acquisition. The goodwill is calculated as the excess of the purchase price over the fair values of the assets acquired and liabilities assumed and has been allocated to the steel products segment (see Note 8). Goodwill recognized for tax purposes was $30.5 million, all of which is deductible for such purposes. Other acquisitions, exclusive of purchase price adjustments of acquisitions made and net of cash acquired, totaled $33.1 million in 2018, $212.7 million in 2017 and $50.1 million in 2016. Included in the 2017 amount is the January 9, 2017 acquisition of Southland Tube, Inc. (“Southland”) and the September 1, 2017 acquisition of St. Louis Cold Drawn, Inc. (“St. Louis Cold Drawn”). Nucor used cash on hand to acquire Southland and St. Louis Cold Drawn for purchase prices of approximately $130 million and $60 million, respectively. Southland is a manufacturer of HSS steel tubing, which is primarily used in nonresidential construction markets. Southland had shipments to external customers of approximately 290,000 tons in 2018 and has one manufacturing facility in Birmingham, Alabama. St. Louis Cold Drawn is a manufacturer of cold drawn rounds, hexagons, squares and special sections that mainly serves the U.S. and Mexican automotive and industrial markets. St. Louis Cold Drawn has two manufacturing locations, one in St. Louis, Missouri and the other in Monterrey, Mexico, that have a combined annual capacity of approximately 200,000 tons. The financial results of Southland and St. Louis Cold Drawn are included as part of the steel products segment (see Note 22).

Short-term Investments

Short-term Investments	12 Months Ended
	Dec. 31, 2018
Text Block [Abstract]
Short-term Investments	4. Short-term Investments Nucor held $50.0 million of short-term investments as of December 31, 2017 (none at December 31, 2018). The investments held as of December 31, 2017 consisted of a certificate of deposit (“CD”) and were classified as available-for-sale. No realized or unrealized gains or losses were incurred in 2018, 2017 or 2016.

Accounts Receivable

Accounts Receivable	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Accounts Receivable	5. Accounts Receivable An allowance for doubtful accounts is maintained for estimated losses resulting from the inability of our customers to make required payments. Accounts receivable are stated net of the allowance for doubtful accounts of $62.1 million at December 31, 2018 ($49.0 million at December 31, 2017 and $45.9 million at December 31, 2016).

Inventories

Inventories	12 Months Ended
	Dec. 31, 2018
Inventory Disclosure [Abstract]
Inventories	6. Inventories Inventories consisted of approximately 43% raw materials and supplies and 57% finished and semi-finished products at December 31, 2018 (42% and 58%, respectively, at December 31, 2017). Nucor’s manufacturing process consists of a continuous, vertically integrated process from which products are sold to customers at various stages throughout the process. Since most steel products can be classified as either finished or semi-finished products, these two categories of inventory are combined.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	7. Property, Plant and Equipment (in thousands) December 31, 2018 2017 Land and improvements $ 654,786 $ 639,878 Buildings and improvements 1,283,182 1,249,350 Machinery and equipment 11,101,840 10,937,416 Proved oil and gas properties 557,383 556,507 Leasehold interest in unproved oil and gas properties 165,000 165,000 Construction in process and equipment deposits 762,884 241,820 14,525,075 13,789,971 Less accumulated depreciation (9,190,327 ) (8,696,824 ) $ 5,334,748 $ 5,093,147 The estimated useful lives primarily range from five to 25 years for land improvements, four to 40 years for buildings and improvements and two to 15 years for machinery and equipment. The useful life for proved oil and gas properties is based on the unit-of-production In September 2018, Nucor performed an impairment analysis of its proved producing natural gas well assets due to the current and projected natural gas pricing environment at our sales point in the Piceance Basin, which continued to deteriorate during 2018. Management was monitoring these assets since the prior impairment analysis that was performed in the fourth quarter of 2017. The projected natural gas pricing at our sales point in the Piceance Basin reached such a level in the third quarter of 2018 that management determined that a triggering event had occurred. One of the main assumptions that most significantly affects the cash flow determination is management’s estimate of future pricing of natural gas and natural gas liquids. The pricing used in this impairment assessment was developed by management based on projected natural gas market supply and demand dynamics, in conjunction with a review of projections by market analysts. The impairment analysis was performed on each of Nucor’s three groups (“fields”) of wells, with each field defined by common geographic location. Two of Nucor’s three fields of wells did not pass the undiscounted cash flow impairment analysis. An after-tax

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	8. Goodwill and Other Intangible Assets The change in the net carrying amount of goodwill for the years ended December 31, 2018 and 2017 by segment is as follows: (in thousands) Steel Mills Steel Raw Total Balance, December 31, 2016 $ 620,156 $ 702,995 $ 729,577 $ 2,052,728 Acquisitions 125,328 7,004 — 132,332 Translation — 10,998 — 10,998 Balance, December 31, 2017 745,484 720,997 729,577 2,196,058 Reclassifications (153,498 ) 153,498 — — Translation — (11,722 ) — (11,722 ) Balance, December 31, 2018 $ 591,986 $ 862,773 $ 729,577 $ 2,184,336 The majority of goodwill is not tax deductible. Intangible assets with estimated useful lives of five to 22 years are amortized on a straight-line or accelerated basis and are comprised of the following: (in thousands) December 31, 2018 December 31, 2017 Gross Accumulated Gross Accumulated Customer relationships $ 1,418,250 $ 713,656 $ 1,420,224 $ 641,089 Trademarks and trade names 176,046 87,680 176,471 77,208 Other 67,820 32,276 62,805 26,557 $ 1,662,116 $ 833,612 $ 1,659,500 $ 744,854 Intangible asset amortization expense was $88.8 million in 2018 ($91.2 million in 2017 and $73.9 million in 2016). Annual amortization expense is estimated to be $87.1 million in 2019, $84.7 million in 2020, $83.5 million in 2021, $81.2 million in 2022 and $80.0 million in 2023. The Company completed its annual goodwill impairment testing as of the first day of the fourth quarters of 2018, 2017 and 2016 and concluded that as of such dates there was no impairment of goodwill for any of its reporting units. The annual evaluation performed in 2018 used forward-looking projections and included significant expected improvements in the future cash flows of one of the Company’s reporting units, Rebar Fabrication. As a result of the rapid and significant increase in the price of steel in 2018, the operating results of this reporting unit declined significantly and remained depressed throughout the remainder of the year. Nucor expects the operating results of this reporting unit to improve when the price of steel in relation to the reporting unit’s backlog pricing stabilizes. The fair value of this reporting unit exceeded its carrying value by approximately 8% in the most recent evaluation. If our assessment of the relevant facts and circumstances changes, or the actual performance in this reporting unit falls short of expected results, noncash impairment charges may be required. Total goodwill associated with the Rebar Fabrication reporting unit as of December 31, 2018 was $353.0 million. An impairment of goodwill may also lead us to record an impairment of other intangible assets. Total finite-lived intangible assets associated with the Rebar Fabrication reporting unit as of December 31, 2018 was $76.7 million. There are no significant historical accumulated impairment charges, by segment or in the aggregate, related to goodwill.

Equity Investments

Equity Investments	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Equity Investments	9. Equity Investments The carrying value of our equity investments in domestic and foreign companies was $869.9 million at December 31, 2018 ($750.1 million at December 31, 2017), and is recorded in other assets in the consolidated balance sheets. NUMIT Nucor owns a 50% economic and voting interest in NuMit LLC (“NuMit”). NuMit owns 100% of the equity interest in Steel Technologies LLC, an operator of 26 sheet processing facilities located throughout the United States, Canada and Mexico. Nucor accounts for the investment in NuMit (on a one-month DUFERDOFIN NUCOR Nucor owns a 50% economic and voting interest in Duferdofin Nucor S.r.l. (“Duferdofin Nucor”), an Italian steel manufacturer, and accounts for the investment (on a one-month Nucor’s investment in Duferdofin Nucor at December 31, 2018 was $269.1 million ($285.9 million at December 31, 2017). Nucor’s 50% share of the total net assets of Duferdofin Nucor was $113.5 million at December 31, 2018, resulting in a basis difference of $155.6 million due to the step-up step-up As of December 31, 2018, Nucor had outstanding notes receivable of €35.0 million ($40.2 million) from Duferdofin Nucor (€35.0 million, or $41.9 million, as of December 31, 2017). The notes receivable bear interest at 0.84% and reset annually on September 30 to the 12-month Nucor has issued a guarantee for its ownership percentage (50%) of Duferdofin Nucor’s borrowings under Facility A of a Structured Trade Finance Facilities Agreement (“Facility A”). The fair value of the guarantee is immaterial. In April 2018, Duferdofin Nucor amended and extended Facility A to mature on April 16, 2021.The maximum amount Duferdofin Nucor could borrow under Facility A was €160.0 million ($183.7 million) at December 31, 2018. As of December 31, 2018, there was €155.0 million ($178.0 million) outstanding under that facility (€122.5 million, or $146.7 million, as of December 31, 2017). If Duferdofin Nucor fails to pay when due any amounts for which it is obligated under Facility A, Nucor could be required to pay 50% of such amounts pursuant to and in accordance with the terms of its guarantee. Any indebtedness of Duferdofin Nucor to Nucor is effectively subordinated to the indebtedness of Duferdofin Nucor under Facility A. Nucor has not recorded any liability associated with this guarantee. NUCOR-JFE Nucor owns a 50% economic and voting interest in Nucor-JFE (“Nucor-JFE”), 50-50 Nucor-JFE Nucor-JFE one-month Nucor-JFE ALL EQUITY INVESTMENTS Nucor reviews its equity investments for impairment if and when circumstances indicate that a decline in value below their carrying amounts may have occurred. Nucor last assessed its equity investment in Duferdofin Nucor for impairment during the fourth quarter of 2017 due to the protracted challenging steel market conditions in Europe. After completing its assessment, the Company determined that the estimated fair value exceeded its carrying amount by a sufficient amount and that there was no need to record an impairment charge. The assumptions that most significantly affect the fair value determination include projected cash flows and the discount rate. It is reasonably possible that material deviation of future performance from the estimates used in our most recent valuation could result in impairment of our investment in Duferdofin Nucor. We will continue to monitor for potential triggering events that could affect the carrying value of our investment in Duferdofin Nucor as a result of future market conditions and any changes in our business strategy.

Current Liabilities

Current Liabilities	12 Months Ended
	Dec. 31, 2018
Payables and Accruals [Abstract]
Current Liabilities	10. Current Liabilities Book overdrafts, included in accounts payable in the consolidated balance sheets, were $89.8 million at December 31, 2018 ($139.2 million at December 31, 2017). Dividends payable, included in accrued expenses and other current liabilities in the consolidated balance sheets, were $123.4 million at December 31, 2018 ($121.8 million at December 31, 2017).

Debt and Other Financing Arrang

Debt and Other Financing Arrangements	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt and Other Financing Arrangements	11. Debt and Other Financing Arrangements (in thousands) December 31, 2018 2017 Industrial revenue bonds due from 2020 to 2040* $ 1,010,600 $ 1,010,600 Notes, 5.85%, due 2018 — 500,000 Notes, 4.125%, due 2022 600,000 600,000 Notes, 4.0%, due 2023 500,000 500,000 Notes, 3.95%, due 2028 500,000 — Notes, 6.40%, due 2037 650,000 650,000 Notes, 5.20%, due 2043 500,000 500,000 Notes, 4.40%, due 2048 500,000 — Total long-term debt 4,260,600 3,760,600 Less debt issuance costs 27,324 18,358 Total amounts outstanding 4,233,276 3,742,242 Less current maturities — 500,000 Total long-term debt due after one year $ 4,233,276 $ 3,242,242 * The industrial revenue bonds had variable rates ranging from 1.88% to 2.03% at December 31, 2018 and 1.65% to 1.92% at December 31, 2017, respectively. Annual aggregate long-term debt maturities are: none in 2019, $20.0 million in 2020, none in 2021, $601.0 million in 2022, $500.0 million in 2023 and $3.14 billion thereafter. In April 2018, Nucor issued $500.0 million of 3.95% notes due 2028 and $500.0 million of 4.40% notes due 2048. Net proceeds of the issuances were $986.1 million, of which $500.0 million was used to repay the $500.0 million of 5.85% notes that matured June 1, 2018. Costs of $11.9 million associated with the issuances have been capitalized and will be amortized over the lives of the notes. During the second quarter of 2018, Nucor amended its $1.50 billion unsecured revolving credit facility to extend the maturity date from April 2021 to April 2023. Costs associated with the amendment were immaterial. The unsecured revolving credit facility provides up to $1.50 billion in revolving loans and allows up to $500.0 million in additional commitments at Nucor’s election in accordance with the terms set forth in the credit agreement. Up to the equivalent of $850.0 million of the credit facility is available for foreign currency loans, up to $100.0 million is available for the issuance of letters of credit and up to $500.0 million is available for the issuance of revolving loans for Nucor subsidiaries in accordance with terms set forth in the credit agreement. The credit facility provides for a pricing grid based upon the credit rating of Nucor’s senior unsecured long-term debt and, alternatively, interest rates quoted by lenders in connection with competitive bidding. The credit facility includes customary financial and other covenants, including a limit on the ratio of funded debt to total capital of 60%, a limit on Nucor’s ability to pledge the Company’s assets and a limit on consolidations, mergers and sales of assets. As of December 31, 2018, Nucor’s funded debt to total capital ratio was 30%, and Nucor was in compliance with all covenants under the credit facility. No borrowings were outstanding under the credit facility as of December 31, 2018 and 2017. Harris Steel has credit facilities totaling approximately $7.5 million, with no outstanding borrowings at December 31, 2018 ($7.8 million at December 31, 2017). In addition, the business of Nucor Trading S.A. is financed by uncommitted trade credit arrangements with a number of European banking institutions. As of December 31, 2018, Nucor Trading S.A. had outstanding borrowings of $57.9 million, which is presented in short-term debt in the consolidated balance sheets ($52.8 million at December 31, 2017). Letters of credit totaling $56.2 million were outstanding as of December 31, 2018 ($40.0 million as of December 31, 2017), related to certain obligations, including workers’ compensation, utilities deposits and credit arrangements by Nucor Trading S.A. for commitments to purchase inventories.

Capital Stock

Capital Stock	12 Months Ended
	Dec. 31, 2018
Text Block [Abstract]
Capital Stock	12. Capital Stock The par value of Nucor’s common stock is $0.40 per share and there are 800 million shares authorized. In addition, 250,000 shares of preferred stock, par value of $4.00 per share, are authorized, with preferences, rights and restrictions as may be fixed by the Board of Directors. There are no shares of preferred stock issued or outstanding. Dividends declared per share were $1.5400 in 2018 ($1.5125 per share in 2017 and $1.5025 per share in 2016). The Company repurchased $854.0 million of its common stock in 2018 ($90.3 million in 2017 and $5.2 million in 2016). On September 6, 2018, the Company announced that the Board of Directors had approved a share repurchase program under which the Company is authorized to repurchase up to $2.0 billion of the Company’s common stock. Share repurchases will be made from time to time in the open market at prevailing market prices, through private transactions or block trades. The timing and amount of repurchases will depend on market conditions, share price, applicable legal requirements and other factors. The share repurchase authorization is discretionary and has no expiration date. The Board of Directors also terminated any previously authorized repurchase programs. At December 31, 2018, the Company had approximately $1.5 billion available for share repurchases under the program.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	13. Derivative Financial Instruments The following tables summarize information regarding Nucor’s derivative instruments (in thousands): Fair Value at Fair Value of Derivative Instruments December 31, Consolidated Balance Sheet Location 2018 2017 Asset derivatives designated as hedging instruments: Commodity contracts Other current assets $ 100 $ — Asset derivatives not designated as hedging instruments: Commodity contracts Other current assets 2,617 — Foreign exchange contracts Other current assets 2,055 479 Total asset derivatives not designated as hedging instruments 4,672 479 Total asset derivatives $ 4,772 $ 479 Liability derivatives designated as hedging instruments: Commodity contracts Accrued expenses and other current liabilities $ — $ (2,100 ) Commodity contracts Deferred credits and other liabilities (8,600 ) (2,400 ) Total liability derivatives designated as hedging instruments (8,600 ) (4,500 ) Liability derivatives not designated as hedging instruments: Commodity contracts Accrued expenses and other current liabilities — (4,031 ) Total liability derivatives $ (8,600 ) $ (8,531 ) The Effect of Derivatives Instruments on the Consolidated Statements of Earnings Derivatives Designated as Hedging Instruments for the Year Ended December 31, (in thousands) Derivatives in Cash Flow Statement of Amount of Gain or (Loss), Amount of Gain or Amount of Gain or (Loss), 2018 2017 2016 2018 2017 2016 2018 2017 2016 Commodity contracts Cost of $ (3,568 ) $ (4,523 ) $ 2,570 $ 132 $ (973 ) $ (9,880 ) $ — $ — $ — Derivatives Not Designated as Hedging Instruments for the Year Ended December 31, (in thousands) Derivatives Not Designated as Hedging Instruments Statement of Earnings Amount of Gain or (Loss) 2018 2017 2016 Commodity contracts Cost of products sold $ 14,572 $ (11,973 ) $ (3,251 ) Foreign exchange contracts Cost of products sold 3,609 (3,344 ) 238 Total $ 18,181 $ (15,317 ) $ (3,013 ) At December 31, 2018, natural gas swaps covering approximately 47.0 million MMBTUs (extending through December 2022) were outstanding.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	14. Fair Value Measurements The following table summarizes information regarding Nucor’s financial assets and liabilities that are measured at fair value as of December 31, 2018 and 2017. Nucor does not have any non-financial (in thousands) Description Carrying Quoted Prices Significant Significant As of December 31, 2018 Assets: Cash equivalents $ 1,084,319 $ 1,084,319 $ — $ — Derivative contracts 4,772 — 4,772 — Total assets $ 1,089,091 $ 1,084,319 $ 4,772 $ — Liabilities: Derivative contracts $ (8,600 ) $ — $ (8,600 ) $ — As of December 31, 2017 Assets: Cash equivalents $ 594,946 $ 594,946 $ — $ — Short-term investments 50,000 50,000 — — Derivative contracts 479 — 479 — Total assets $ 645,425 $ 644,946 $ 479 $ — Liabilities: Derivative contracts $ (8,531 ) $ — $ (8,531 ) $ — Fair value measurements for Nucor’s cash equivalents and short-term investments are classified under Level 1 because such measurements are based on quoted market prices in active markets for identical assets. Fair value measurements for Nucor’s derivatives, which are typically commodity or foreign exchange contracts, are classified under Level 2 because such measurements are based on published market prices for similar assets or are estimated based on published market prices for similar assets or are estimated based on observable inputs such as interest rates, yield curves, credit risks, spot and future commodity prices and spot and future exchange rates. There were no transfers between levels in the fair value hierarchy for the periods presented. The fair value of short-term and long-term debt, including current maturities, was approximately $4.45 billion at December 31, 2018 (approximately $4.19 billion at December 31, 2017). The debt fair value estimates are classified under Level 2 because such estimates are based on readily available market prices of our debt at December 31, 2018 and 2017, or similar debt with the same maturities, ratings and interest rates.

Contingencies

Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Contingencies	15. Contingencies Nucor is subject to environmental laws and regulations established by federal, state and local authorities and, accordingly, makes provisions for the estimated costs of compliance. Of the undiscounted total of $18.4 million of accrued environmental costs at December 31, 2018 ($17.1 million at December 31, 2017), $7.0 million was classified in accrued expenses and other current liabilities ($3.8 million at December 31, 2017) and $11.4 million was classified in deferred credits and other liabilities ($13.3 million at December 31, 2017). Inherent uncertainties exist in these estimates primarily due to unknown conditions, evolving remediation technology and changing governmental regulations and legal standards. We are from time to time a party to various lawsuits, claims and legal proceedings that arise in the ordinary course of business. With respect to all such lawsuits, claims and proceedings, we record reserves when it is probable a liability has been incurred and the amount of loss can be reasonably estimated. We do not believe that any of these proceedings, individually or in the aggregate, would be expected to have a material adverse effect on our results of operations, financial position or cash flows. Nucor maintains liability insurance with self-insurance limits for certain risks.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	16. Stock-Based Compensation Overview The Company maintains the Nucor Corporation 2014 Omnibus Incentive Compensation Plan (the “Omnibus Plan”) under which the Company may award stock-based compensation to key employees, officers and non-employee The Company also maintains a number of inactive plans under which stock-based awards remain outstanding but no further awards may be made. As of December 31, 2018, 1.9 million shares were reserved for issuance upon the future settlement of outstanding awards under such inactive plans. Stock Options Stock options may be granted to Nucor’s key employees, officers and non-employee A summary of activity under Nucor’s stock option plans is as follows (shares in thousands): 2018 2017 2016 Year Ended December 31, Shares Weighted - Shares Weighted - Shares Weighted - Number of shares under option: Outstanding at beginning of year 4,106 $ 47.96 3,591 $ 45.32 3,092 $ 43.51 Granted 265 $ 65.80 698 $ 59.07 899 $ 48.80 Exercised (543 ) $ 44.33 (183 ) $ 38.56 (400 ) $ 39.19 Canceled — — — — — — Outstanding at end of year 3,828 $ 49.71 4,106 $ 47.96 3,591 $ 45.32 Options exercisable at end of year 2,112 $ 45.41 1,809 $ 43.39 1,557 $ 40.80 The total intrinsic value of stock options (the amount by which the stock price exceeded the exercise price of the stock option on the date of exercise) that were exercised during 2018 was $12.6 million ($4.5 million in 2017 and $6.8 million in 2016). The following table summarizes information about stock options outstanding at December 31, 2018 (shares in thousands): Options Outstanding Options Exercisable Range of Exercise Prices Number Weighted- Weighted- Number Weighted- $35.00 - $45.00 967 3.7 years $ 40.31 967 $ 40.31 45.01 - 55.00 1,897 6.7 years $ 48.81 1,064 $ 48.81 55.01 - 65.00 698 8.4 years $ 59.07 48 $ 59.07 65.01 - 75.00 266 9.4 years $ 65.80 33 $ 65.80 $35.00 - $75.00 3,828 6.4 years $ 49.71 2,112 $ 45.41 As of December 31, 2018, the total aggregate intrinsic value of stock options outstanding and stock options exercisable was $16.8 million and $14.3 million, respectively. The grant date fair value of stock options granted was $15.07 per share in 2018 ($12.61 per share in 2017 and $9.12 per share in 2016). The fair value was estimated using the Black-Scholes option-pricing model with the following assumptions: 2018 2017 2016 Exercise price $ 65.80 $ 59.07 $ 48.80 Expected dividend yield 2.31 % 2.56 % 3.07 % Expected stock price volatility 25.28 % 26.53 % 26.14 % Risk-free interest rate 2.85 % 2.02 % 1.67 % Expected life (in years) 6.5 6.5 6.5 Stock options granted to employees who are eligible for retirement on the date of grant are expensed immediately since these awards vest upon retirement from the Company. Retirement, for purposes of vesting in these stock options, means termination of employment after satisfying age and years of service requirements. Similarly, stock options granted to employees who will become retirement-eligible prior to the end of the vesting term are expensed over the period through which the employee will become retirement-eligible. Compensation expense for stock options granted to employees who will not become retirement-eligible prior to the end of the vesting term is recognized on a straight-line basis over the vesting period. Compensation expense for stock options was $4.6 million in 2018 ($8.2 million in 2017 and $7.8 million in 2016). As of December 31, 2018, unrecognized compensation expense related to stock options was $1.6 million, which is expected to be recognized over a weighted-average period of 1.7 years. Restricted Stock Units Nucor annually grants restricted stock units (“RSUs”) to key employees, officers and non-employee non-employee non-employee RSUs granted to employees who are eligible for retirement on the date of grant are expensed immediately, and RSUs granted to employees who will become retirement-eligible prior to the end of the vesting term are expensed over the period through which the employee will become retirement-eligible since these awards vest upon retirement from the Company. Compensation expense for RSUs granted to employees who will not become retirement-eligible prior to the end of the vesting term is recognized on a straight-line basis over the vesting period. Cash dividend equivalents are paid to holders of RSUs each quarter. Dividend equivalents paid on RSUs expected to vest are recognized as a reduction in retained earnings. The fair value of an RSU is determined based on the closing price of Nucor’s common stock on the date of the grant. A summary of Nucor’s RSU activity is as follows (shares in thousands): 2018 2017 2016 Grant Date Grant Date Grant Date Year Ended December 31, Shares Fair Value Shares Fair Value Shares Fair Value Restricted stock units: Unvested at beginning of year 1,071 $ 52.62 1,040 $ 48.47 1,031 $ 47.93 Granted 1,013 $ 65.80 721 $ 59.07 723 $ 48.80 Vested (827 ) $ 58.98 (677 ) $ 53.17 (681 ) $ 48.09 Canceled (11 ) $ 55.02 (13 ) $ 50.21 (33 ) $ 46.44 Unvested at end of year 1,246 $ 59.09 1,071 $ 52.62 1,040 $ 48.47 Compensation expense for RSUs was $54.3 million in 2018 ($38.0 million in 2017 and $33.9 million in 2016). The total fair value of shares vested during 2018 was $54.4 million ($39.9 million in 2017 and $33.4 million in 2016). As of December 31, 2018, unrecognized compensation expense related to unvested RSUs was $46.7 million, which is expected to be recognized over a weighted-average period of 1.7 years. Restricted Stock Awards Prior to their expiration effective December 31, 2017, the Nucor Corporation Senior Officers Long-Term Incentive Plan and the Nucor Corporation Senior Officers Annual Incentive Plan authorized the award of shares of common stock to officers subject to certain conditions and restrictions. Effective January 1, 2018, the Company adopted supplements to the Omnibus Plan with terms that permit the award of shares of common stock to officers subject to the conditions and restrictions described below, which are substantially similar to those of the expired Senior Officers Long-Term Incentive Plan and Senior Officers Annual Incentive Plan. The expired Senior Officers Long-Term Incentive Plan, together with the applicable supplement, is referred to below as the “LTIP,” and the expired Senior Officers Annual Incentive Plan, together with the applicable supplement, is referred to below as the “AIP.” The LTIP provides for the award of shares of restricted common stock at the end of each LTIP performance measurement period at no cost to officers if certain financial performance goals are met during the period. One-third The AIP provides for the payment of annual cash incentive awards. An AIP participant may elect, however, to defer payment of up to one-half A summary of Nucor’s restricted stock activity under the AIP and the LTIP is as follows (shares in thousands): 2018 2017 2016 Grant Date Grant Date Grant Date Year Ended December 31, Shares Fair Value Shares Fair Value Shares Fair Value Restricted stock awards and units: Unvested at beginning of year 91 $ 54.50 67 $ 45.77 63 $ 48.07 Granted 256 $ 67.68 172 $ 60.62 123 $ 44.03 Vested (217 ) $ 64.95 (148 ) $ 51.72 (116 ) $ 45.16 Canceled — — — — (3 ) $ 45.75 Unvested at end of year 130 $ 62.97 91 $ 54.50 67 $ 45.77 Compensation expense for common stock and common stock units awarded under the AIP and the LTIP is recorded over the performance measurement and vesting periods based on the anticipated number and market value of shares of common stock and common stock units to be awarded. Compensation expense for anticipated awards based upon Nucor’s financial performance, exclusive of amounts payable in cash, was $14.6 million in 2018 ($17.9 million in 2017 and $14.8 million in 2016). The total fair value of shares vested during 2018 was $14.7 million ($9.0 million in 2017 and $5.2 million in 2016). As of December 31, 2018, unrecognized compensation expense related to unvested restricted stock awards was $1.6 million, which is expected to be recognized over a weighted-average period of 1.7 years.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Employee Benefit Plans	17. Employee Benefit Plans Nucor makes contributions to a Profit Sharing and Retirement Savings Plan for qualified employees based on the profitability of the Company. Nucor’s expense for these benefits totaled $307.9 million in 2018 ($169.4 million in 2017 and $129.0 million in 2016). The related liability for these benefits is included in salaries, wages and related accruals in the consolidated balance sheets. Nucor also has a medical plan covering certain eligible early retirees. The unfunded obligation, included in deferred credits and other liabilities in the consolidated balance sheets, totaled $25.5 million at December 31, 2018 ($25.1 million at December 31, 2017). The expense associated with this early retiree medical plan totaled $2.1 million in 2018 ($2.2 million in 2017 and $0.6 million in 2016). The discount rate is used by Nucor in determining its benefit obligation and was 4.24% in 2018 (3.6% in 2017 and 4.2% in 2016). The health care cost increase trend rate used was 6.3% in 2018 (6.6% in 2017 and 6.8% in 2016). The health care cost increase in the trend rate is projected to decline gradually to 4.5% by 2037.

Interest Expense (Income)

Interest Expense (Income)	12 Months Ended
	Dec. 31, 2018
Banking and Thrift, Interest [Abstract]
Interest Expense (Income)	18. Interest Expense (Income) The components of net interest expense are as follows (in thousands): Year Ended December 31, 2018 2017 2016 Interest expense $ 161,256 $ 187,282 $ 181,179 Interest income (25,721 ) (13,702 ) (11,935 ) Interest expense, net $ 135,535 $ 173,580 $ 169,244 Interest paid was $165.7 million in 2018 ($186.8 million in 2017 and $183.4 million in 2016). Interest expense for 2018 decreased compared to 2017 in part due to a benefit received from entering into and settling a treasury lock instrument in anticipation of the Company’s debt issuance in the second quarter of 2018. The Company did not elect hedge accounting for this instrument.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	19. Income Taxes The Tax Reform Act made significant changes to U.S. tax law that impacted the Company, including permanently lowering the U.S. corporate federal income tax rate from 35% to 21% and the elimination of the domestic manufacturing deduction effective for tax years beginning after December 31, 2017. The Tax Reform Act also included a one-time low-taxed The staff of the U.S. Securities and Exchange Commission issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of Accounting Standards Codification 740, Income Taxes, in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Reform Act. Reflected in our 2017 financial results, and in accordance with SAB 118, were certain provisional income tax effects of the 2017 Tax Reform Act, including a net $175.2 million of tax benefit recorded primarily due to the revaluation of our U.S. net deferred tax liabilities from 35% to 21%. The Company, provisionally, did not include any tax impact related to the transition tax in its consolidated financial statements for the year ended December 31, 2017. In 2018, upon completion of its 2017 federal tax return, Nucor finalized the analysis of the previously estimated one-time Components of earnings (losses) from continuing operations before income taxes and noncontrolling interests are as follows (in thousands): Year Ended December 31, 2018 2017 2016 United States $ 3,160,111 $ 1,610,652 $ 1,241,117 Foreign 69,280 139,305 57,542 $ 3,229,391 $ 1,749,957 $ 1,298,659 The provision for income taxes consists of the following (in thousands): Year Ended December 31, 2018 2017 2016 Current: Federal $ 633,868 $ 504,865 $ 286,224 State 96,622 37,308 27,353 Foreign 14,800 48,386 13,211 Total current 745,290 590,559 326,788 Deferred: Federal 4,953 (207,006 ) 71,777 State 6,847 (4,533 ) 5,193 Foreign (8,783 ) (9,634 ) (5,515 ) Total deferred 3,017 (221,173 ) 71,455 Total provision for income taxes $ 748,307 $ 369,386 $ 398,243 A reconciliation of the federal statutory tax rate (21% in 2018 and 35% in 2017 and 2016) to the total provision is as follows: Year Ended December 31, 2018 2017 2016 Taxes computed at statutory rate 21.00 % 35.00 % 35.00 % State income taxes, net of federal income tax benefit 2.52 % 1.22 % 1.67 % Federal research credit -0.14 % -0.24 % -0.28 % Domestic manufacturing deduction 0.00 % -2.58 % -2.11 % Equity in losses of foreign joint venture 0.08 % 0.13 % 0.27 % Foreign rate differential -0.07 % -0.62 % -1.05 % Noncontrolling interests -0.78 % -1.24 % -2.81 % Tax Reform Act 0.18 % -10.01 % 0.00 % Out-of-period correction 0.00 % 0.00 % -0.22 % Other, net 0.38 % -0.55 % 0.20 % Provision for income taxes 23.17 % 21.11 % 30.67 % For the year ended December 31, 2018 the effective tax rate on continuing operations increased 2.06% versus the prior year period to 23.17%. The increase in rate between 2017 and 2018 is primarily due to the increase in the effective rate for state income taxes and the write-off (-2.58% (-10.01%) Deferred tax assets and liabilities resulted from the following (in thousands): December 31, 2018 2017 Deferred tax assets: Accrued liabilities and reserves $ 128,553 $ 127,955 Allowance for doubtful accounts 20,134 15,136 Inventory 63,950 61,522 Post-retirement benefits 8,746 9,167 Commodity hedges 1,393 2,056 Net operating loss carryforward 27,131 19,895 Tax credit carryforwards 16,792 92,380 Other deferred tax assets 779 — Valuation allowance (30,104 ) (96,107 ) Total deferred tax assets 237,374 232,004 Deferred tax liabilities: Holdbacks and amounts not due under contracts $ (10,731 ) $ (10,214 ) Intangibles (167,374 ) (164,716 ) Property, plant and equipment (390,575 ) (385,815 ) Total deferred tax liabilities (568,680 ) (560,745 ) Total net deferred tax liabilities $ (331,306 ) $ (328,741 ) On August 9, 2018, the Treasury Department issued regulations on the one-time Non-current Non-current The Tax Reform Act provided for a one-time State net operating loss carryforwards were $483.0 million at December 31, 2018 ($605.9 million at December 31, 2017). If unused, they will expire between 2019 and 2038. Foreign net operating loss carryforwards were $58.6 million at December 31, 2018 ($28.3 million at December 31, 2017). If unused, they will expire between 2029 and 2037. At December 31, 2018, Nucor had approximately $48.6 million of unrecognized tax benefits, of which $48.0 million would affect Nucor’s effective tax rate, if recognized. At December 31, 2017, Nucor had approximately $48.8 million of unrecognized tax benefits, of which $48.2 million would affect Nucor’s effective tax rate, if recognized. A reconciliation of the beginning and ending amounts of unrecognized tax benefits recorded in deferred credits and other liabilities is as follows (in thousands): December 31, 2018 2017 2016 Balance at beginning of year $ 48,845 $ 44,088 $ 50,510 Additions based on tax positions related to current year 16,424 11,154 6,157 Reductions based on tax positions related to current year — — — Additions based on tax positions related to prior years 199 2,556 147 Reductions based on tax positions related to prior years (8,198 ) (5,461 ) (8,201 ) Reductions due to settlements with taxing authorities (2,160 ) — (258 ) Reductions due to statute of limitations lapse (6,505 ) (3,492 ) (4,267 ) Balance at end of year $ 48,605 $ 48,845 $ 44,088 We estimate that in the next twelve months, our gross uncertain tax positions, exclusive of interest, could decrease by as much as $7.4 million, as a result of the expiration of the statute of limitations. During 2018, Nucor recognized $4.0 million of benefit in interest and penalties ($2.2 million of benefit in 2017 and $2.8 million of benefit in 2016). The interest and penalties are included in interest expense and other expenses, respectively, in the consolidated statements of earnings. As of December 31, 2018, Nucor had approximately $11.2 million of accrued interest and penalties related to uncertain tax positions on the consolidated balance sheet (approximately $16.1 million at December 31, 2017). Nucor has concluded U.S. federal income tax matters for years through 2014. The tax years 2015 through 2017 remain open to examination by the Internal Revenue Service. The Canada Revenue Agency has concluded its examination of the 2012 and 2013 Canadian returns for Harris Steel Group Inc. and certain related affiliates. The 2015 tax year is currently under examination by the Canadian Revenue Agency. In January 2019, the Trinidad and Tobago Inland Revenue Division initiated an audit of the Nu-Iron

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	20. Accumulated Other Comprehensive Income (Loss) The following tables reflect the changes in accumulated other comprehensive income (loss) by component (in thousands): Gains and (Losses) on Foreign Currency Adjustment to Early Hedging Derivatives Gains (Losses) Retiree Medical Plan Total December 31, 2017 $ (2,800 ) $ (257,513 ) $ $ (254,681 ) Other comprehensive income (loss) before reclassifications (3,568 ) (47,133 ) 1,731 (48,970 ) Amounts reclassified from accumulated other comprehensive income (loss) into earnings (1) (132 ) — (350 ) (482 ) Net current-period other comprehensive income (loss) (3,700 ) (47,133 ) 1,381 (49,452 ) December 31, 2018 $ (6,500 ) $ (304,646 ) $ $ (304,133 ) (1) Includes ($132) and ($350) net-of-tax Gains and Losses on Foreign Currency Adjustment to Early Hedging Derivatives Gains (Losses) Retiree Medical Plan Total December 31, 2016 $ 750 $ (326,170 ) $ 7,577 $ (317,843 ) Other comprehensive income (loss) before reclassifications (4,523 ) 68,657 (1,530 ) 62,604 Amounts reclassified from accumulated other comprehensive income (loss) into earnings (2) 973 — (415 ) 558 Net current-period other comprehensive income (loss) (3,550 ) 68,657 (1,945 ) 63,162 December 31, 2017 $ (2,800 ) $ (257,513 ) $ 5,632 $ (254,681 ) (2) Includes $973 and ($415) net-of-tax

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share	21. Earnings Per Share The computations of basic and diluted net earnings per share are as follows (in thousands, except per share data): Year Ended December 31, 2018 2017 2016 Basic net earnings per share: Basic net earnings $ 2,360,767 $ 1,318,688 $ 796,271 Earnings allocated to participating securities (9,344 ) (4,549 ) (2,632 ) Net earnings available to common stockholders $ 2,351,423 $ 1,314,139 $ 793,639 Average shares outstanding 315,858 319,990 319,563 Basic net earnings per share $ 7.44 $ 4.11 $ 2.48 Diluted net earnings per share: Diluted net earnings $ 2,360,767 $ 1,318,688 $ 796,271 Earnings allocated to participating securities (9,317 ) (4,539 ) (2,631 ) Net earnings available to common stockholders $ 2,351,450 $ 1,314,149 $ 793,640 Diluted average shares outstanding: Basic shares outstanding 315,858 319,990 319,563 Dilutive effect of stock options and other 875 783 259 316,733 320,773 319,822 Diluted net earnings per share $ 7.42 $ 4.10 $ 2.48 The following stock options were excluded from the computation of diluted net earnings per share because their effect would have been anti-dilutive (shares in thousands): Year Ended December 31, 2018 2017 2016 Anti-dilutive stock options: Weighted-average shares 156 407 942 Weighted-average exercise price $ 65.80 $ 59.07 $ 47.04

Segments

Segments	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segments	22. Segments Nucor reports its results in the following segments: steel mills, steel products and raw materials. The steel mills segment includes carbon and alloy steel in sheet, bars, structural and plate; steel trading businesses; rebar distribution businesses; and Nucor’s equity method investments in Duferdofin Nucor, NuMit and Nucor-JFE. Nu-Iron Previously, Nucor’s tubular products and piling products businesses were reported in the steel mills segment. In the first quarter of 2018, these businesses were reclassified to the steel products segment as part of a realignment of Nucor’s reportable segments to reflect the way in which they are now viewed by management and how segment performance assessments will be made by the chief operating decision maker beginning in such period. The segment data for the comparable periods has also been reclassified into the steel products segment in order to conform to the current year presentation. Additionally, the composition of assets by segment for the comparable periods was reclassified to conform to the current year presentation. This reclassification between segments did not have any impact on the consolidated asset balances. Net interest expense, other income, profit sharing expense and stock-based compensation are shown under Corporate/eliminations. Corporate assets primarily include cash and cash equivalents, short-term investments, allowances to eliminate intercompany profit in inventory, deferred income tax assets, federal and state income taxes receivable and investments in and advances to affiliates. Nucor’s results by segment are as follows (in thousands): Year Ended December 31, 2018 2017 2016 Net sales to external customers: Steel mills $ 16,245,218 $ 12,929,709 $ 10,546,847 Steel products 6,796,501 5,579,744 4,452,649 Raw materials 2,025,560 1,742,940 1,208,626 $ 25,067,279 $ 20,252,393 $ 16,208,122 Intercompany sales: Steel mills $ 3,924,160 $ 2,916,017 $ 2,066,547 Steel products 207,003 118,249 110,368 Raw materials 11,460,645 9,191,081 5,997,498 Corporate/eliminations (15,591,808 ) (12,225,347 ) (8,174,413 ) $ — $ — $ — Depreciation expense: Steel mills $ 378,146 $ 377,210 $ 368,859 Steel products 80,681 76,992 45,674 Raw materials 161,666 172,699 191,466 Corporate 10,386 8,932 7,193 $ 630,879 $ 635,833 $ 613,192 Amortization expense: Steel mills $ 9,400 $ 9,706 $ 7,632 Steel products 51,997 52,597 36,845 Raw materials 27,361 28,925 29,385 $ 88,758 $ 91,228 $ 73,862 Earnings (loss) before income taxes and noncontrolling interests: Steel mills $ 3,500,085 $ 1,953,075 $ 1,680,156 Steel products 467,105 337,978 294,039 Raw materials 236,241 129,296 (95,121 ) Corporate/eliminations (974,040 ) (670,392 ) (580,415 ) $ 3,229,391 $ 1,749,957 $ 1,298,659 Segment assets: Steel mills $ 9,244,086 $ 7,671,217 $ 6,980,979 Steel products 4,734,636 4,323,907 3,651,118 Raw materials 3,492,126 3,396,110 3,235,237 Corporate/eliminations 449,740 450,024 1,356,184 $ 17,920,588 $ 15,841,258 $ 15,223,518 Capital expenditures: Steel mills $ 720,310 $ 336,760 $ 357,545 Steel products 88,585 90,952 49,149 Raw materials 169,926 59,036 194,112 Corporate 18,435 20,326 16,871 $ 997,256 $ 507,074 $ 617,677 Net sales by product were as follows (in thousands). Further product group breakdown is impracticable. Year Ended December 31, 2018 2017 2016 Net sales to external customers: Sheet $ 7,571,765 $ 6,407,974 $ 5,178,467 Bar 4,709,292 3,558,806 2,886,648 Structural 1,830,476 1,317,995 1,277,547 Plate 2,133,685 1,644,934 1,204,185 Tubular Products 1,347,577 917,235 60,106 Rebar Fabrication 1,496,194 1,306,418 1,272,338 Other Steel Products 3,952,730 3,356,091 3,120,205 Raw Materials 2,025,560 1,742,940 1,208,626 $ 25,067,279 $ 20,252,393 $ 16,208,122

Revenue

Revenue	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue	23. Revenue Revenue is recognized when obligations under the terms of contracts with our customers are satisfied; generally, this occurs upon shipment or when control is transferred. Revenue is measured as the amount of consideration expected to be received in exchange for transferring the goods. In addition, revenue is deferred when cash payments are received or due in advance of performance. The durations of Nucor’s contracts with customers are generally one year or less. Customer payment terms are generally 30 days. Contract liabilities are primarily related to deferred revenue resulting from cash payments received in advance from customers to protect against credit risk. Contract liabilities totaled $91.2 million as of December 31, 2018 ($72.3 million as of December 31, 2017), and are included in accrued expenses and other current liabilities in the consolidated balance sheets. The amount of revenue reclassified from the December 31, 2017 contract liabilities balance during 2018 was approximately $61.3 million. The following table disaggregates our net sales by major source for 2018 (in thousands): Year Ended December 31, 2018 Steel Mills Steel Products Raw Materials Total Sheet $ 7,571,765 $ — $ — $ 7,571,765 Bar 4,709,292 — — 4,709,292 Structural 1,830,476 — — 1,830,476 Plate 2,133,685 — — 2,133,685 Tubular Products — 1,347,577 — 1,347,577 Rebar Fabrication — 1,496,194 — 1,496,194 Other Steel Products — 3,952,730 — 3,952,730 Raw Materials — — 2,025,560 2,025,560 $ 16,245,218 $ 6,796,501 $ 2,025,560 $ 25,067,279 STEEL MILLS SEGMENT Sheet – For the majority of sheet products, we transfer control and recognize a sale when we ship the product from the sheet mill to our customer. The amount of consideration we receive and revenue we recognize for spot market sales are based upon prevailing prices at the time of sale. The amount of consideration we receive and revenue we recognize for contract customers are based primarily on pricing formulae that permit price adjustments to reflect changes in the current market-based indices and/or raw material costs near the time of shipment. The amount of tons sold to contract customers at any given time depends on a variety of factors, including our consideration of current and future market conditions, our strategy to appropriately balance spot and contract tons in a manner to meet our customers’ requirements while considering the expected profitability, our desire to sustain a diversified customer base and our end-use Bar, Structural and Plate – For the majority of bar, structural and plate products, we transfer control and recognize a sale when we ship the product from the mill to our customer. The significant majority of bar, structural and plate product sales are spot market sales, and the amount of consideration we receive and revenue we recognize for those sales are based upon prevailing prices at the time of sale. STEEL PRODUCTS SEGMENT Tubular Products – The tubular products businesses transfer control and recognize a sale when the product is shipped from our operating locations to our customers. The significant majority of tubular product sales are spot market sales, and the amount of consideration we receive and revenue we recognize for those sales are based upon prevailing prices at the time of sale. Rebar Fabrication – The majority of revenue for our rebar fabrication businesses relates to revenue from contracts with customers for the supply of fabricated rebar. For the majority of these transactions, we transfer control and recognize a sale when the products are shipped from our operating locations and collection is reasonably assured. Provisions for losses on incomplete contracts are made in the period in which such losses are determined. Our rebar fabrication businesses also generate a significant amount of revenue from contracts with customers in which they supply fabricated rebar and install it at the customer’s job site. There are two performance obligations for these types of contracts: the supply of the fabricated rebar and the installation of the supplied rebar at the customer’s job site. For the supply of fabricated rebar performance obligation, we transfer control and recognize a sale when the product is delivered to our customer’s job site. The transaction price allocated to this performance obligation is determined at the start of the contract, based on the then current market price for supplied fabricated rebar. For the installation of supplied rebar performance obligation, we transfer control and recognize a sale when the delivered material is installed. The transaction price allocated to this performance obligation is determined at the start of the contract, based on the then current market price for the installation of fabricated rebar. Variable consideration occurring from change orders and price escalations caused by changes in underlying material costs for previously satisfied performance obligations are recognized cumulatively in the period in which management believes that the amount of consideration is changed and collection is reasonably assured. Management reviews these situations on a case-by-case Other Steel Products – Other steel products include our joist, deck, cold finish, metal building systems, piling and the other remaining businesses that comprise the steel products segment. Generally for these businesses, we transfer control and recognize a sale when we ship the product from our operating locations to our customers. The amount of consideration we receive and revenue we recognize for those sales are agreed upon with the customers before the product is shipped. RAW MATERIALS SEGMENT The majority of the raw materials segment revenue from outside customers is generated by The David J. Joseph Company and its affiliates. We transfer control and recognize a sale based on the terms of the agreement with the customer, which is generally when the product has met the delivery requirements. The amount of consideration we receive and revenue we recognize for those sales is based on the contract with the customer, which generally reflects current market prices at the time the contract is entered into.

Quarterly Information (Unaudite

Quarterly Information (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Information (Unaudited)	24. Quarterly Information (Unaudited) (in thousands, except per share data) Year Ended December 31, 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Net sales $ 5,568,419 $ 6,460,774 $ 6,742,202 $ 6,295,884 Gross margin (1) 726,406 1,166,590 1,290,150 1,112,262 Net earnings (2) 380,112 713,615 706,287 681,070 Net earnings attributable to Nucor stockholders (2) 354,179 683,153 676,656 646,779 Net earnings per share: Basic $ 1.11 $ 2.14 $ 2.13 $ 2.08 Diluted $ 1.10 $ 2.13 $ 2.13 $ 2.07 (in thousands, except per share data) Year Ended December 31, 2017 First Quarter Second Quarter Third Quarter Fourth Quarter Net sales $ 4,815,179 $ 5,174,769 $ 5,170,117 $ 5,092,328 Gross margin (3) 760,250 709,625 578,964 520,568 Net earnings (4) 377,648 341,724 266,105 395,094 Net earnings attributable to Nucor stockholders (4) 356,899 323,048 254,850 383,891 Net earnings per share: Basic $ 1.11 $ 1.00 $ 0.79 $ 1.20 Diluted $ 1.11 $ 1.00 $ 0.79 $ 1.20 (1) Second quarter results include a benefit of $9.6 million related to insurance recoveries. Third quarter results include a benefit of $18.0 million related to insurance recoveries. (2) First quarter results include the write off of deferred tax assets of $21.8 million due to the change in the tax status of a subsidiary. Second quarter results include a benefit of $23.3 million (which includes the amount in gross margin) related to insurance recoveries. Third quarter results include a non-cash (3) First quarter results include inventory-related purchase accounting charges of $9.8 million related to the acquisition of Southland and Republic. (4) Third quarter results include a net benefit of $13.2 million related to tax return true-ups

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents are recorded at cost plus accrued interest, which approximates fair value, and have original maturities of three months or less at the date of purchase. Cash and cash equivalents are maintained primarily with a few high-credit quality financial institutions.
Short-term Investments	Short-term Investments Short-term investments are recorded at cost plus accrued interest, which approximates fair value. Unrealized gains and losses on investments classified as available-for-sale re-evaluates
Inventories	Inventories Inventories are stated at the lower of cost or market. The Company records any amount required to reduce the carrying value of inventory to net realizable value as a charge to cost of products sold. Scrap and scrap substitute costs are a very significant component of the raw material, semi-finished and finished product inventory balances. The vast majority of the Company’s inventory is recorded on the first-in, first-out
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment is stated at cost, except for property, plant and equipment acquired through acquisitions which is recorded at acquisition date fair value. With the exception of our natural gas wells, depreciation is provided on a straight-line basis over the estimated useful lives of the assets. Depletion of all capitalized costs associated with our natural gas producing properties is expensed on a unit-of-production
Goodwill and Other Intangibles	Goodwill and Other Intangibles Goodwill is the excess of cost over the fair value of net assets of businesses acquired. Goodwill is not amortized but is tested annually for impairment and whenever events or circumstances change that would make it more likely than not that an impairment may have occurred. We perform our annual impairment analysis as of the first day of the fourth quarter each year. The evaluation of impairment involves comparing the current estimated fair value of each reporting unit, which is a level below the reportable segment, to the recorded value, including goodwill. When appropriate, Nucor performs a qualitative assessment to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. For certain reporting units, it is necessary to perform a quantitative analysis. In these instances, a discounted cash flow model is used to determine the current estimated fair value of these reporting units. A number of significant assumptions and estimates are involved in the application of the discounted cash flow model to forecast operating cash flows, which could include market growth and market share, sales volumes and prices, costs to produce, discount rate and estimated capital needs. Management considers historical experience and all available information at the time the fair values of its reporting units are estimated. Assumptions in estimating future cash flows are subject to a high degree of judgment and complexity. Changes in assumptions and estimates may affect the fair value of goodwill and could result in impairment charges in future periods. Finite-lived intangible assets are amortized over their estimated useful lives on a straight-line or accelerated basis.
Long-Lived Asset Impairments	Long-Lived Asset Impairments We evaluate our property, plant and equipment and finite-lived intangible assets for potential impairment on an individual asset basis or at the lowest level asset grouping for which independent cash flows can be separately identified. Asset impairments are assessed whenever circumstances indicate that the carrying amounts of those productive assets could exceed their projected undiscounted cash flows. When it is determined that impairment exists, the related assets are written down to their estimated fair market value.
Equity Method Investments	Equity Method Investments Investments in joint ventures in which Nucor shares control over the financial and operating decisions but in which Nucor is not the primary beneficiary are accounted for under the equity method. Each of the Company’s equity method investments is subject to a review for impairment if, and when, circumstances indicate that a decline in value below its carrying amount may have occurred. Examples of such circumstances include, but are not limited to, a significant deterioration in the earnings performance or business prospects of the investee; missed financial projections; a significant adverse change in the regulatory, economic or technological environment of the investee; a significant adverse change in the general market condition of either the geographic area or the industry in which the investee operates; and recurring negative cash flows from operations. When management considers the decline to be other than temporary, the related investment is written down to its estimated fair market value.
Derivative Financial Instruments	Derivative Financial Instruments Nucor periodically uses derivative financial instruments primarily to partially manage its exposure to price risk related to natural gas purchases used in the production process as well as its exposure to scrap, copper and aluminum purchased for resale to its customers. In addition, Nucor periodically uses derivatives to partially manage its exposure to changes in interest rates on outstanding debt instruments and uses forward foreign exchange contracts to hedge cash flows associated with certain assets and liabilities, firm commitments and anticipated transactions. Nucor recognizes all derivative instruments in the consolidated balance sheets at fair value. Amounts included in accumulated other comprehensive income (loss) related to cash flow hedges are reclassified into earnings when the underlying transaction is recognized in net earnings. Changes in fair value hedges are reported in earnings along with changes in the fair value of the hedged items. When cash flow and fair value hedges affect net earnings, they are included on the same financial statement line as the underlying transaction (cost of products sold or interest expense). If these instruments do not meet hedge accounting criteria, the change in fair value (or a portion thereof) is recognized immediately in earnings in the same financial statement line as the underlying transaction.
Revenue Recognition	Revenue Recognition Nucor recognizes revenue when obligations under the terms of contracts with our customers are satisfied; generally, this occurs upon shipment or when control is transferred. Revenue is measured as the amount of consideration expected to be received in exchange for transferring the goods. In addition, revenue is deferred when cash payments are received or due in advance of performance. See Note 23 for further information.
Income Taxes	Income Taxes Nucor utilizes the liability method of accounting for income taxes. Under the liability method, deferred taxes are determined based on the temporary differences between the financial statement and tax basis of assets and liabilities using tax rates expected to be in effect during the years in which the basis differences reverse. A valuation allowance is recorded when it is more likely than not that some of the deferred tax assets will not be realized. Nucor recognizes the effect of income tax positions only if those positions are more likely than not of being sustained. Potential accrued interest and penalties related to unrecognized tax benefits are recognized as a component of interest expense and other expenses. The staff of the U.S. Securities and Exchange Commission issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of Accounting Standards Codification 740, Income Taxes, in situations when a registrant does not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Reform Act. Reflected in our 2017 financial results, and in accordance with SAB 118, were certain provisional income tax effects of the Tax Reform Act. Adjustments, as allowed for under SAB 118, to these provisional amounts were made in 2018. The accounting for the Tax Reform Act was completed in the fourth quarter of 2018. Further information on the tax impacts of the Tax Reform Act is included in Note 19 of the Company’s consolidated financial statements.
Stock-Based Compensation	Stock-Based Compensation The Company recognizes the cost of stock-based compensation as an expense using fair value measurement methods. The assumptions used to calculate the fair value of stock-based compensation granted are evaluated and revised for new grants, as necessary, to reflect market conditions and experience.
Foreign Currency Translation	Foreign Currency Translation For Nucor’s operations where the functional currency is other than the U.S. dollar, assets and liabilities have been translated at year-end
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In the first quarter of 2018, Nucor adopted new accounting guidance related to revenue recognition for all contracts using the modified retrospective method. The modified retrospective method requires that the cumulative effect of initially applying this new guidance be recorded as an adjustment to the opening balance of retained earnings in the consolidated balance sheet. The adoption of this new accounting guidance did not have an impact on any prior period earnings attributable to Nucor stockholders, and no adjustment was recorded to the opening retained earnings balance as of January 1, 2018. Retrospective adjustment of comparative prior period information is not required when using the modified retrospective adoption method, and no comparative prior periods have been adjusted for the new guidance. The adoption of the new revenue accounting guidance did not significantly change the way we recognize revenue. To illustrate this, if we had continued using the previous accounting guidance in effect before the adoption of the new revenue accounting guidance, our consolidated net sales for 2018 would have increased approximately $81.4 million, or 0.3%, and cost of products sold would have increased by the same amount. There would have been no impact on any other financial statement line items in the consolidated financial statements for 2018. See Note 23 for disclosures required by the new revenue accounting guidance. In the first quarter of 2018, Nucor adopted new accounting guidance regarding the recognition and measurement of financial assets and financial liabilities. Changes to the current accounting guidance primarily affect the accounting for equity investments, financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. In addition, the Financial Accounting Standards Board clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale In the first quarter of 2018, Nucor adopted new accounting guidance regarding the presentation and classification of certain cash receipts and cash payments in the statement of cash flows. The new guidance addresses specific cash flow presentation issues in order to reduce diversity in existing practice. The adoption of this new guidance did not have a material impact on the Company’s consolidated financial statements. In the first quarter of 2018, Nucor adopted new accounting guidance regarding intra-entity transfers of assets other than inventory. The new guidance requires that an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The adoption of this new guidance did not have a material impact on the Company’s consolidated financial statements.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, new accounting guidance was issued regarding the accounting for leases. The new guidance requires all lessees to recognize on the balance sheet right to use assets and lease liabilities for the rights and obligations created by lease arrangements with terms greater than 12 months. The new guidance is effective for the Company for annual and interim reporting periods beginning after December 15, 2018. In July 2018, this accounting guidance was amended to permit companies to recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption and to continue reporting comparative periods prior to adoption in accordance with current lease guidance. The Company will adopt this new guidance in the first quarter of 2019 and will record a cumulative adjustment to the January 1, 2019 retained earnings balance. While the adoption of this new guidance is expected to increase assets and liabilities due to the recognition of lease rights and obligations on the Company’s consolidated balance sheet effective January 1, 2019, the Company does not expect the adoption of this new guidance to have a significant impact on its consolidated financial statements. In February 2018, new accounting guidance was issued regarding the tax effects of the Tax Reform Act. The new guidance allows for a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Reform Act to improve the usefulness of information reported to financial statement users. The new guidance is effective for the Company for annual and interim reporting periods beginning after December 15, 2018. The Company does not expect the adoption of this new guidance to have a material impact on its consolidated financial statements.

Acquisitions and Dispositions (

Acquisitions and Dispositions (Tables)	12 Months Ended
	Dec. 31, 2018
Republic [Member]
Fair Values of Assets Acquired and Liabilities Assumed	The following table summarizes the fair values of the assets acquired and liabilities assumed of Republic as of the date of acquisition (in thousands): Cash $ 206 Accounts receivable 39,177 Inventory 33,561 Other current assets 1,101 Property, plant and equipment 67,412 Goodwill 115,562 Other intangible assets 89,200 Other assets 3,118 Total assets acquired 349,337 Current liabilities 17,743 Total liabilities assumed 17,743 Net assets acquired $ 331,594
Purchase Price Allocation of Identifiable Intangible Assets	The following table summarizes the purchase price allocation to the identifiable intangible assets of Republic as of the date of acquisition (in thousands, except years): Weighted - Customer relationships $ 80,800 12 years Trademarks and trade names 8,400 13 years $ 89,200
ITC [Member]
Fair Values of Assets Acquired and Liabilities Assumed	The following table summarizes the fair values of the assets acquired and liabilities assumed of ITC as of the date of acquisition (in thousands): Cash $ 1,058 Accounts receivable 33,173 Inventory 94,400 Other current assets 1,743 Property, plant and equipment 177,668 Goodwill 29,522 Other intangible assets 130,900 Other assets 1,287 Total assets acquired 469,751 Current liabilities 39,633 Total liabilities assumed 39,633 Net assets acquired $ 430,118
Purchase Price Allocation of Identifiable Intangible Assets	The following table summarizes the purchase price allocation to the identifiable intangible assets of ITC as of the date of acquisition (in thousands, except years): Weighted - Customer relationships $ 119,000 15 years Trademarks and trade names 7,100 15 years Other 4,800 5 years $ 130,900

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	(in thousands) December 31, 2018 2017 Land and improvements $ 654,786 $ 639,878 Buildings and improvements 1,283,182 1,249,350 Machinery and equipment 11,101,840 10,937,416 Proved oil and gas properties 557,383 556,507 Leasehold interest in unproved oil and gas properties 165,000 165,000 Construction in process and equipment deposits 762,884 241,820 14,525,075 13,789,971 Less accumulated depreciation (9,190,327 ) (8,696,824 ) $ 5,334,748 $ 5,093,147

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Change in Net Carrying Amount of Goodwill by Segment	The change in the net carrying amount of goodwill for the years ended December 31, 2018 and 2017 by segment is as follows: (in thousands) Steel Mills Steel Raw Total Balance, December 31, 2016 $ 620,156 $ 702,995 $ 729,577 $ 2,052,728 Acquisitions 125,328 7,004 — 132,332 Translation — 10,998 — 10,998 Balance, December 31, 2017 745,484 720,997 729,577 2,196,058 Reclassifications (153,498 ) 153,498 — — Translation — (11,722 ) — (11,722 ) Balance, December 31, 2018 $ 591,986 $ 862,773 $ 729,577 $ 2,184,336
Schedule of Intangible Assets	Intangible assets with estimated useful lives of five to 22 years are amortized on a straight-line or accelerated basis and are comprised of the following: (in thousands) December 31, 2018 December 31, 2017 Gross Accumulated Gross Accumulated Customer relationships $ 1,418,250 $ 713,656 $ 1,420,224 $ 641,089 Trademarks and trade names 176,046 87,680 176,471 77,208 Other 67,820 32,276 62,805 26,557 $ 1,662,116 $ 833,612 $ 1,659,500 $ 744,854

Debt and Other Financing Arra_2

Debt and Other Financing Arrangements (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Debt and Other Financing Arrangements	(in thousands) December 31, 2018 2017 Industrial revenue bonds due from 2020 to 2040* $ 1,010,600 $ 1,010,600 Notes, 5.85%, due 2018 — 500,000 Notes, 4.125%, due 2022 600,000 600,000 Notes, 4.0%, due 2023 500,000 500,000 Notes, 3.95%, due 2028 500,000 — Notes, 6.40%, due 2037 650,000 650,000 Notes, 5.20%, due 2043 500,000 500,000 Notes, 4.40%, due 2048 500,000 — Total long-term debt 4,260,600 3,760,600 Less debt issuance costs 27,324 18,358 Total amounts outstanding 4,233,276 3,742,242 Less current maturities — 500,000 Total long-term debt due after one year $ 4,233,276 $ 3,242,242 * The industrial revenue bonds had variable rates ranging from 1.88% to 2.03% at December 31, 2018 and 1.65% to 1.92% at December 31, 2017, respectively.

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Values of Derivative Instruments	The following tables summarize information regarding Nucor’s derivative instruments (in thousands): Fair Value at Fair Value of Derivative Instruments December 31, Consolidated Balance Sheet Location 2018 2017 Asset derivatives designated as hedging instruments: Commodity contracts Other current assets $ 100 $ — Asset derivatives not designated as hedging instruments: Commodity contracts Other current assets 2,617 — Foreign exchange contracts Other current assets 2,055 479 Total asset derivatives not designated as hedging instruments 4,672 479 Total asset derivatives $ 4,772 $ 479 Liability derivatives designated as hedging instruments: Commodity contracts Accrued expenses and other current liabilities $ — $ (2,100 ) Commodity contracts Deferred credits and other liabilities (8,600 ) (2,400 ) Total liability derivatives designated as hedging instruments (8,600 ) (4,500 ) Liability derivatives not designated as hedging instruments: Commodity contracts Accrued expenses and other current liabilities — (4,031 ) Total liability derivatives $ (8,600 ) $ (8,531 )
Derivatives Designated as Hedging Instrument [Member]
Effect of Derivatives Instruments on Consolidated Statements of Earnings	The Effect of Derivatives Instruments on the Consolidated Statements of Earnings Derivatives Designated as Hedging Instruments for the Year Ended December 31, (in thousands) Derivatives in Cash Flow Statement of Amount of Gain or (Loss), Amount of Gain or Amount of Gain or (Loss), 2018 2017 2016 2018 2017 2016 2018 2017 2016 Commodity contracts Cost of $ (3,568 ) $ (4,523 ) $ 2,570 $ 132 $ (973 ) $ (9,880 ) $ — $ — $ —
Derivatives Not Designated as Hedging Instrument [Member]
Effect of Derivatives Instruments on Consolidated Statements of Earnings	Derivatives Not Designated as Hedging Instruments for the Year Ended December 31, (in thousands) Derivatives Not Designated as Hedging Instruments Statement of Earnings Amount of Gain or (Loss) 2018 2017 2016 Commodity contracts Cost of products sold $ 14,572 $ (11,973 ) $ (3,251 ) Foreign exchange contracts Cost of products sold 3,609 (3,344 ) 238 Total $ 18,181 $ (15,317 ) $ (3,013 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value	The following table summarizes information regarding Nucor’s financial assets and liabilities that are measured at fair value as of December 31, 2018 and 2017. Nucor does not have any non-financial (in thousands) Description Carrying Quoted Prices Significant Significant As of December 31, 2018 Assets: Cash equivalents $ 1,084,319 $ 1,084,319 $ — $ — Derivative contracts 4,772 — 4,772 — Total assets $ 1,089,091 $ 1,084,319 $ 4,772 $ — Liabilities: Derivative contracts $ (8,600 ) $ — $ (8,600 ) $ — As of December 31, 2017 Assets: Cash equivalents $ 594,946 $ 594,946 $ — $ — Short-term investments 50,000 50,000 — — Derivative contracts 479 — 479 — Total assets $ 645,425 $ 644,946 $ 479 $ — Liabilities: Derivative contracts $ (8,531 ) $ — $ (8,531 ) $ —

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Plans Activity	A summary of activity under Nucor’s stock option plans is as follows (shares in thousands): 2018 2017 2016 Year Ended December 31, Shares Weighted - Shares Weighted - Shares Weighted - Number of shares under option: Outstanding at beginning of year 4,106 $ 47.96 3,591 $ 45.32 3,092 $ 43.51 Granted 265 $ 65.80 698 $ 59.07 899 $ 48.80 Exercised (543 ) $ 44.33 (183 ) $ 38.56 (400 ) $ 39.19 Canceled — — — — — — Outstanding at end of year 3,828 $ 49.71 4,106 $ 47.96 3,591 $ 45.32 Options exercisable at end of year 2,112 $ 45.41 1,809 $ 43.39 1,557 $ 40.80
Summary of Stock Options Outstanding	The following table summarizes information about stock options outstanding at December 31, 2018 (shares in thousands): Options Outstanding Options Exercisable Range of Exercise Prices Number Weighted- Weighted- Number Weighted- $35.00 - $45.00 967 3.7 years $ 40.31 967 $ 40.31 45.01 - 55.00 1,897 6.7 years $ 48.81 1,064 $ 48.81 55.01 - 65.00 698 8.4 years $ 59.07 48 $ 59.07 65.01 - 75.00 266 9.4 years $ 65.80 33 $ 65.80 $35.00 - $75.00 3,828 6.4 years $ 49.71 2,112 $ 45.41
Schedule of Grant Date Fair Value Black-Scholes Option-Pricing Model Assumptions	The fair value was estimated using the Black-Scholes option-pricing model with the following assumptions: 2018 2017 2016 Exercise price $ 65.80 $ 59.07 $ 48.80 Expected dividend yield 2.31 % 2.56 % 3.07 % Expected stock price volatility 25.28 % 26.53 % 26.14 % Risk-free interest rate 2.85 % 2.02 % 1.67 % Expected life (in years) 6.5 6.5 6.5
Summary of Nucor's RSU Activity	A summary of Nucor’s RSU activity is as follows (shares in thousands): 2018 2017 2016 Grant Date Grant Date Grant Date Year Ended December 31, Shares Fair Value Shares Fair Value Shares Fair Value Restricted stock units: Unvested at beginning of year 1,071 $ 52.62 1,040 $ 48.47 1,031 $ 47.93 Granted 1,013 $ 65.80 721 $ 59.07 723 $ 48.80 Vested (827 ) $ 58.98 (677 ) $ 53.17 (681 ) $ 48.09 Canceled (11 ) $ 55.02 (13 ) $ 50.21 (33 ) $ 46.44 Unvested at end of year 1,246 $ 59.09 1,071 $ 52.62 1,040 $ 48.47
Summary of Nucor's Restricted Stock Activity under AIP and LTIP	A summary of Nucor’s restricted stock activity under the AIP and the LTIP is as follows (shares in thousands): 2018 2017 2016 Grant Date Grant Date Grant Date Year Ended December 31, Shares Fair Value Shares Fair Value Shares Fair Value Restricted stock awards and units: Unvested at beginning of year 91 $ 54.50 67 $ 45.77 63 $ 48.07 Granted 256 $ 67.68 172 $ 60.62 123 $ 44.03 Vested (217 ) $ 64.95 (148 ) $ 51.72 (116 ) $ 45.16 Canceled — — — — (3 ) $ 45.75 Unvested at end of year 130 $ 62.97 91 $ 54.50 67 $ 45.77

Interest Expense (Income) (Tabl

Interest Expense (Income) (Tables)	12 Months Ended
	Dec. 31, 2018
Banking and Thrift, Interest [Abstract]
Schedule of Components of Net Interest Expense	The components of net interest expense are as follows (in thousands): Year Ended December 31, 2018 2017 2016 Interest expense $ 161,256 $ 187,282 $ 181,179 Interest income (25,721 ) (13,702 ) (11,935 ) Interest expense, net $ 135,535 $ 173,580 $ 169,244

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Components of Earnings (Losses) from Continuing Operations Before Income Taxes and Noncontrolling Interests	Components of earnings (losses) from continuing operations before income taxes and noncontrolling interests are as follows (in thousands): Year Ended December 31, 2018 2017 2016 United States $ 3,160,111 $ 1,610,652 $ 1,241,117 Foreign 69,280 139,305 57,542 $ 3,229,391 $ 1,749,957 $ 1,298,659
Provision for Income Taxes	The provision for income taxes consists of the following (in thousands): Year Ended December 31, 2018 2017 2016 Current: Federal $ 633,868 $ 504,865 $ 286,224 State 96,622 37,308 27,353 Foreign 14,800 48,386 13,211 Total current 745,290 590,559 326,788 Deferred: Federal 4,953 (207,006 ) 71,777 State 6,847 (4,533 ) 5,193 Foreign (8,783 ) (9,634 ) (5,515 ) Total deferred 3,017 (221,173 ) 71,455 Total provision for income taxes $ 748,307 $ 369,386 $ 398,243
Reconciliation of the Federal Statutory Tax Rate to Total Provisions	A reconciliation of the federal statutory tax rate (21% in 2018 and 35% in 2017 and 2016) to the total provision is as follows: Year Ended December 31, 2018 2017 2016 Taxes computed at statutory rate 21.00 % 35.00 % 35.00 % State income taxes, net of federal income tax benefit 2.52 % 1.22 % 1.67 % Federal research credit -0.14 % -0.24 % -0.28 % Domestic manufacturing deduction 0.00 % -2.58 % -2.11 % Equity in losses of foreign joint venture 0.08 % 0.13 % 0.27 % Foreign rate differential -0.07 % -0.62 % -1.05 % Noncontrolling interests -0.78 % -1.24 % -2.81 % Tax Reform Act 0.18 % -10.01 % 0.00 % Out-of-period correction 0.00 % 0.00 % -0.22 % Other, net 0.38 % -0.55 % 0.20 % Provision for income taxes 23.17 % 21.11 % 30.67 %
Deferred Tax Assets and Liabilities	Deferred tax assets and liabilities resulted from the following (in thousands): December 31, 2018 2017 Deferred tax assets: Accrued liabilities and reserves $ 128,553 $ 127,955 Allowance for doubtful accounts 20,134 15,136 Inventory 63,950 61,522 Post-retirement benefits 8,746 9,167 Commodity hedges 1,393 2,056 Net operating loss carryforward 27,131 19,895 Tax credit carryforwards 16,792 92,380 Other deferred tax assets 779 — Valuation allowance (30,104 ) (96,107 ) Total deferred tax assets 237,374 232,004 Deferred tax liabilities: Holdbacks and amounts not due under contracts $ (10,731 ) $ (10,214 ) Intangibles (167,374 ) (164,716 ) Property, plant and equipment (390,575 ) (385,815 ) Total deferred tax liabilities (568,680 ) (560,745 ) Total net deferred tax liabilities $ (331,306 ) $ (328,741 )
Reconciliation of the Beginning and Ending Amounts of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amounts of unrecognized tax benefits recorded in deferred credits and other liabilities is as follows (in thousands): December 31, 2018 2017 2016 Balance at beginning of year $ 48,845 $ 44,088 $ 50,510 Additions based on tax positions related to current year 16,424 11,154 6,157 Reductions based on tax positions related to current year — — — Additions based on tax positions related to prior years 199 2,556 147 Reductions based on tax positions related to prior years (8,198 ) (5,461 ) (8,201 ) Reductions due to settlements with taxing authorities (2,160 ) — (258 ) Reductions due to statute of limitations lapse (6,505 ) (3,492 ) (4,267 ) Balance at end of year $ 48,605 $ 48,845 $ 44,088

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Components of Accumulated Other Comprehensive Income (Loss)	The following tables reflect the changes in accumulated other comprehensive income (loss) by component (in thousands): Gains and (Losses) on Foreign Currency Adjustment to Early Hedging Derivatives Gains (Losses) Retiree Medical Plan Total December 31, 2017 $ (2,800 ) $ (257,513 ) $ $ (254,681 ) Other comprehensive income (loss) before reclassifications (3,568 ) (47,133 ) 1,731 (48,970 ) Amounts reclassified from accumulated other comprehensive income (loss) into earnings (1) (132 ) — (350 ) (482 ) Net current-period other comprehensive income (loss) (3,700 ) (47,133 ) 1,381 (49,452 ) December 31, 2018 $ (6,500 ) $ (304,646 ) $ $ (304,133 ) (1) Includes ($132) and ($350) net-of-tax Gains and Losses on Foreign Currency Adjustment to Early Hedging Derivatives Gains (Losses) Retiree Medical Plan Total December 31, 2016 $ 750 $ (326,170 ) $ 7,577 $ (317,843 ) Other comprehensive income (loss) before reclassifications (4,523 ) 68,657 (1,530 ) 62,604 Amounts reclassified from accumulated other comprehensive income (loss) into earnings (2) 973 — (415 ) 558 Net current-period other comprehensive income (loss) (3,550 ) 68,657 (1,945 ) 63,162 December 31, 2017 $ (2,800 ) $ (257,513 ) $ 5,632 $ (254,681 ) (2) Includes $973 and ($415) net-of-tax

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Computations of Basic and Diluted Net Earnings Per Share	The computations of basic and diluted net earnings per share are as follows (in thousands, except per share data): Year Ended December 31, 2018 2017 2016 Basic net earnings per share: Basic net earnings $ 2,360,767 $ 1,318,688 $ 796,271 Earnings allocated to participating securities (9,344 ) (4,549 ) (2,632 ) Net earnings available to common stockholders $ 2,351,423 $ 1,314,139 $ 793,639 Average shares outstanding 315,858 319,990 319,563 Basic net earnings per share $ 7.44 $ 4.11 $ 2.48 Diluted net earnings per share: Diluted net earnings $ 2,360,767 $ 1,318,688 $ 796,271 Earnings allocated to participating securities (9,317 ) (4,539 ) (2,631 ) Net earnings available to common stockholders $ 2,351,450 $ 1,314,149 $ 793,640 Diluted average shares outstanding: Basic shares outstanding 315,858 319,990 319,563 Dilutive effect of stock options and other 875 783 259 316,733 320,773 319,822 Diluted net earnings per share $ 7.42 $ 4.10 $ 2.48
Anti-dilutive Stock Options	The following stock options were excluded from the computation of diluted net earnings per share because their effect would have been anti-dilutive (shares in thousands): Year Ended December 31, 2018 2017 2016 Anti-dilutive stock options: Weighted-average shares 156 407 942 Weighted-average exercise price $ 65.80 $ 59.07 $ 47.04

Segments (Tables)

Segments (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segments	Nucor’s results by segment are as follows (in thousands): Year Ended December 31, 2018 2017 2016 Net sales to external customers: Steel mills $ 16,245,218 $ 12,929,709 $ 10,546,847 Steel products 6,796,501 5,579,744 4,452,649 Raw materials 2,025,560 1,742,940 1,208,626 $ 25,067,279 $ 20,252,393 $ 16,208,122 Intercompany sales: Steel mills $ 3,924,160 $ 2,916,017 $ 2,066,547 Steel products 207,003 118,249 110,368 Raw materials 11,460,645 9,191,081 5,997,498 Corporate/eliminations (15,591,808 ) (12,225,347 ) (8,174,413 ) $ — $ — $ — Depreciation expense: Steel mills $ 378,146 $ 377,210 $ 368,859 Steel products 80,681 76,992 45,674 Raw materials 161,666 172,699 191,466 Corporate 10,386 8,932 7,193 $ 630,879 $ 635,833 $ 613,192 Amortization expense: Steel mills $ 9,400 $ 9,706 $ 7,632 Steel products 51,997 52,597 36,845 Raw materials 27,361 28,925 29,385 $ 88,758 $ 91,228 $ 73,862 Earnings (loss) before income taxes and noncontrolling interests: Steel mills $ 3,500,085 $ 1,953,075 $ 1,680,156 Steel products 467,105 337,978 294,039 Raw materials 236,241 129,296 (95,121 ) Corporate/eliminations (974,040 ) (670,392 ) (580,415 ) $ 3,229,391 $ 1,749,957 $ 1,298,659 Segment assets: Steel mills $ 9,244,086 $ 7,671,217 $ 6,980,979 Steel products 4,734,636 4,323,907 3,651,118 Raw materials 3,492,126 3,396,110 3,235,237 Corporate/eliminations 449,740 450,024 1,356,184 $ 17,920,588 $ 15,841,258 $ 15,223,518 Capital expenditures: Steel mills $ 720,310 $ 336,760 $ 357,545 Steel products 88,585 90,952 49,149 Raw materials 169,926 59,036 194,112 Corporate 18,435 20,326 16,871 $ 997,256 $ 507,074 $ 617,677
Schedule of Net Sale by Product to External Customers	Net sales by product were as follows (in thousands). Further product group breakdown is impracticable. Year Ended December 31, 2018 2017 2016 Net sales to external customers: Sheet $ 7,571,765 $ 6,407,974 $ 5,178,467 Bar 4,709,292 3,558,806 2,886,648 Structural 1,830,476 1,317,995 1,277,547 Plate 2,133,685 1,644,934 1,204,185 Tubular Products 1,347,577 917,235 60,106 Rebar Fabrication 1,496,194 1,306,418 1,272,338 Other Steel Products 3,952,730 3,356,091 3,120,205 Raw Materials 2,025,560 1,742,940 1,208,626 $ 25,067,279 $ 20,252,393 $ 16,208,122

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Schedule of Net Sales Disaggregates by Major Source	The following table disaggregates our net sales by major source for 2018 (in thousands): Year Ended December 31, 2018 Steel Mills Steel Products Raw Materials Total Sheet $ 7,571,765 $ — $ — $ 7,571,765 Bar 4,709,292 — — 4,709,292 Structural 1,830,476 — — 1,830,476 Plate 2,133,685 — — 2,133,685 Tubular Products — 1,347,577 — 1,347,577 Rebar Fabrication — 1,496,194 — 1,496,194 Other Steel Products — 3,952,730 — 3,952,730 Raw Materials — — 2,025,560 2,025,560 $ 16,245,218 $ 6,796,501 $ 2,025,560 $ 25,067,279

Quarterly Information (Unaudi_2

Quarterly Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Information	(in thousands, except per share data) Year Ended December 31, 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Net sales $ 5,568,419 $ 6,460,774 $ 6,742,202 $ 6,295,884 Gross margin (1) 726,406 1,166,590 1,290,150 1,112,262 Net earnings (2) 380,112 713,615 706,287 681,070 Net earnings attributable to Nucor stockholders (2) 354,179 683,153 676,656 646,779 Net earnings per share: Basic $ 1.11 $ 2.14 $ 2.13 $ 2.08 Diluted $ 1.10 $ 2.13 $ 2.13 $ 2.07 (in thousands, except per share data) Year Ended December 31, 2017 First Quarter Second Quarter Third Quarter Fourth Quarter Net sales $ 4,815,179 $ 5,174,769 $ 5,170,117 $ 5,092,328 Gross margin (3) 760,250 709,625 578,964 520,568 Net earnings (4) 377,648 341,724 266,105 395,094 Net earnings attributable to Nucor stockholders (4) 356,899 323,048 254,850 383,891 Net earnings per share: Basic $ 1.11 $ 1.00 $ 0.79 $ 1.20 Diluted $ 1.11 $ 1.00 $ 0.79 $ 1.20 (1) Second quarter results include a benefit of $9.6 million related to insurance recoveries. Third quarter results include a benefit of $18.0 million related to insurance recoveries. (2) First quarter results include the write off of deferred tax assets of $21.8 million due to the change in the tax status of a subsidiary. Second quarter results include a benefit of $23.3 million (which includes the amount in gross margin) related to insurance recoveries. Third quarter results include a non-cash (3) First quarter results include inventory-related purchase accounting charges of $9.8 million related to the acquisition of Southland and Republic. (4) Third quarter results include a net benefit of $13.2 million related to tax return true-ups

Nature of Operations and Basi_2

Nature of Operations and Basis of Presentation - Additional Information (Detail)	Dec. 31, 2018
Nucor-Yamato Steel Company [Member]
Summary Of Organization And Operations [Line Items]
Noncontrolling interest, ownership percentage by parent	51.00%

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Accounting Policies [Abstract]
Cash equivalents original maturity period	Three months or less
Amount of increase in consolidated net sales if previous accounting guidance had continued to be used	$ 81.4
Amount of increase in revenue had previous accounting method been used as a percentage of sales	0.30%
Amount of increase in consolidated cost of products sold if previous accounting guidance had continued to be used	$ 81.4

Acquisitions and Dispositions -

Acquisitions and Dispositions - Additional Information (Detail) $ in Thousands	Sep. 01, 2017USD ($)FacilityT	Jan. 20, 2017USD ($)FacilityT	Jan. 09, 2017USD ($)Facility	Oct. 31, 2016USD ($)FacilityT	Dec. 31, 2018USD ($)T	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Business Acquisition [Line Items]
Goodwill					$ 2,184,336	$ 2,196,058	$ 2,052,728
Republic [Member]
Business Acquisition [Line Items]
Business acquisition approximate purchase price		$ 331,600
Approximate annual shipment tons | T		140,000
Number of manufacturing facilities | Facility		2
Goodwill		$ 115,562
ITC [Member]
Business Acquisition [Line Items]
Business acquisition approximate purchase price				$ 430,100
Number of manufacturing facilities | Facility				4
Goodwill				$ 29,522
Annual production capacity | T				860,000
ITC [Member] | Alabama [Member]
Business Acquisition [Line Items]
Number of manufacturing facilities | Facility				2
ITC [Member] | Illinois [Member]
Business Acquisition [Line Items]
Number of manufacturing facilities | Facility				2
Other Acquisitions [Member]
Business Acquisition [Line Items]
Business acquisition approximate purchase price					$ 33,100	212,700	50,100
Southland [Member]
Business Acquisition [Line Items]
Business acquisition approximate purchase price			$ 130,000
Southland [Member] | External Customers [Member]
Business Acquisition [Line Items]
Approximate annual shipment tons | T					290,000
Southland [Member] | Alabama [Member]
Business Acquisition [Line Items]
Number of manufacturing facilities | Facility			1
St. Louis Cold Drawn, Inc. [Member]
Business Acquisition [Line Items]
Business acquisition approximate purchase price	$ 60,000
Approximate annual shipment tons | T	200,000
Number of manufacturing facilities | Facility	2
St. Louis Cold Drawn, Inc. [Member] | St Louis Missouri [Member]
Business Acquisition [Line Items]
Number of manufacturing facilities | Facility	1
St. Louis Cold Drawn, Inc. [Member] | Monterrey, Mexico [Member]
Business Acquisition [Line Items]
Number of manufacturing facilities | Facility	1
Steel Products [Member]
Business Acquisition [Line Items]
Goodwill					$ 862,773	$ 720,997	$ 702,995
Steel Products [Member] | Republic [Member]
Business Acquisition [Line Items]
Goodwill		115,600
Goodwill expected to be deductible for tax purposes		$ 118,600
Steel Products [Member] | ITC [Member]
Business Acquisition [Line Items]
Goodwill				$ 29,500
Goodwill expected to be deductible for tax purposes				$ 30,500

Acquisitions and Dispositions_2

Acquisitions and Dispositions - Fair Values of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Jan. 20, 2017	Dec. 31, 2016	Oct. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 2,184,336	$ 2,196,058		$ 2,052,728
Republic [Member]
Business Acquisition [Line Items]
Cash			$ 206
Accounts receivable			39,177
Inventory			33,561
Other current assets			1,101
Property, plant and equipment			67,412
Goodwill			115,562
Other intangible assets			89,200
Other assets			3,118
Total assets acquired			349,337
Current liabilities			17,743
Total liabilities assumed			17,743
Net assets acquired			$ 331,594
ITC [Member]
Business Acquisition [Line Items]
Cash					$ 1,058
Accounts receivable					33,173
Inventory					94,400
Other current assets					1,743
Property, plant and equipment					177,668
Goodwill					29,522
Other intangible assets					130,900
Other assets					1,287
Total assets acquired					469,751
Current liabilities					39,633
Total liabilities assumed					39,633
Net assets acquired					$ 430,118

Acquisitions and Dispositions_3

Acquisitions and Dispositions - Purchase Price Allocation of Identifiable Intangible Assets (Detail) - USD ($) $ in Thousands	Jan. 20, 2017	Oct. 31, 2016
Republic [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 89,200
Republic [Member] | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 80,800
Weighted - Average Life	12 years
Republic [Member] | Trademarks and Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 8,400
Weighted - Average Life	13 years
ITC [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets		$ 130,900
ITC [Member] | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets		$ 119,000
Weighted - Average Life		15 years
ITC [Member] | Trademarks and Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets		$ 7,100
Weighted - Average Life		15 years
ITC [Member] | Other [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets		$ 4,800
Weighted - Average Life		5 years

Short-term Investments - Additi

Short-term Investments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Short-term Investments [Abstract]
Short-term investments held	$ 0	$ 50,000,000
Realized or unrealized gains or losses	$ 0	$ 0	$ 0

Accounts Receivable - Additiona

Accounts Receivable - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable, Net [Abstract]
Allowance for doubtful accounts receivable	$ 62.1	$ 49	$ 45.9

Inventories - Additional Inform

Inventories - Additional Information (Detail)	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials and supplies in inventory, percentage	43.00%	42.00%
Finished and semi-finished products in inventory, percentage	57.00%	58.00%

Property, Plant and Equipment -

Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 14,525,075	$ 13,789,971
Less accumulated depreciation	(9,190,327)	(8,696,824)
Property, plant and equipment, net, total	5,334,748	5,093,147
Land and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	654,786	639,878
Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,283,182	1,249,350
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,101,840	10,937,416
Proved Oil and Gas Properties [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	557,383	556,507
Leasehold Interest in Unproved Oil and Gas Properties [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	165,000	165,000
Construction in Process and Equipment Deposits [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 762,884	$ 241,820

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 29, 2018	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net		$ 5,334,748	$ 5,093,147
Impairment of assets		$ 110,000
Carrying Value of Two Field of Wells [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	$ 71,000
Impairment of assets	110,000
Carrying Value of Third Field of Wells [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	$ 51,800
Land and Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives range		5 years
Land and Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives range		25 years
Buildings and Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives range		4 years
Buildings and Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives range		40 years
Machinery and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives range		2 years
Machinery and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives range		15 years

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Schedule of Change in Net Carrying Amount of Goodwill by Segment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Balance, beginning of period	$ 2,196,058	$ 2,052,728
Acquisitions		132,332
Translation	(11,722)	10,998
Balance, end of period	2,184,336	2,196,058
Steel Mills [Member]
Goodwill [Line Items]
Balance, beginning of period	745,484	620,156
Reclassifications	(153,498)
Acquisitions		125,328
Balance, end of period	591,986	745,484
Steel Products [Member]
Goodwill [Line Items]
Balance, beginning of period	720,997	702,995
Reclassifications	153,498
Acquisitions		7,004
Translation	(11,722)	10,998
Balance, end of period	862,773	720,997
Raw Materials [Member]
Goodwill [Line Items]
Balance, beginning of period	729,577	729,577
Balance, end of period	$ 729,577	$ 729,577

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended			12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite And Indefinite Lived Intangible Assets [Line Items]
Intangible asset amortization expense				$ 88,800,000	$ 91,200,000	$ 73,900,000
Future amortization expense, in 2019	$ 87,100,000			87,100,000
Future amortization expense, in 2020	84,700,000			84,700,000
Future amortization expense, in 2021	83,500,000			83,500,000
Future amortization expense, in 2022	81,200,000			81,200,000
Future amortization expense, in 2023	80,000,000			80,000,000
Impairment of goodwill	0	$ 0	$ 0
Goodwill	2,184,336,000	2,196,058,000	$ 2,052,728,000	2,184,336,000	2,196,058,000	$ 2,052,728,000
Finite-lived intangible assets	828,504,000	$ 914,646,000		$ 828,504,000	$ 914,646,000
Rebar Fabrication [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Percentage of fair value exceeded carrying value				8.00%
Goodwill	353,000,000			$ 353,000,000
Finite-lived intangible assets	$ 76,700,000			$ 76,700,000
Minimum [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Intangible assets, useful life				5 years
Maximum [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Intangible assets, useful life				22 years

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Amount	$ 1,662,116	$ 1,659,500
Intangible assets, Accumulated Amortization	833,612	744,854
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Amount	1,418,250	1,420,224
Intangible assets, Accumulated Amortization	713,656	641,089
Trademarks and Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Amount	176,046	176,471
Intangible assets, Accumulated Amortization	87,680	77,208
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Amount	67,820	62,805
Intangible assets, Accumulated Amortization	$ 32,276	$ 26,557

Equity Investments - Additional

Equity Investments - Additional Information (Detail) $ in Thousands, € in Millions	12 Months Ended
	Dec. 31, 2018USD ($)Sheet	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2018EUR (€)	Dec. 31, 2017EUR (€)
Schedule of Equity Method Investments [Line Items]
Equity method investment	$ 869,900	$ 750,100
Distributions from affiliates	30,196	49,295	$ 40,602
Amortization expense due to fair value step-up	88,758	91,228	73,862
NuMit LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment	$ 337,200	321,400
Equity method investment, ownership percentage	50.00%			50.00%
Period used for lag basis, in months	1 month
Distributions from affiliates	$ 29,200	48,300	38,600
Steel Technologies LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	100.00%			100.00%
Number of sheet processing facilities operated by Steel Technologies | Sheet	26
Duferdofin Nucor S.r.l. [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment	$ 269,100	285,900
Equity method investment, ownership percentage	50.00%			50.00%
Period used for lag basis, in months	1 month
Equity method investments, share of net assets	$ 113,500
Basis difference due to the step-up to fair value of certain assets and liabilities	155,600
Step-up to fair value of equity method investment, portion related to identification of goodwill	88,500
Amortization expense due to fair value step-up	9,300	8,900	$ 8,800
Due from related parties, noncurrent	$ 40,200	41,900		€ 35	€ 35
Notes receivable, related parties, interest rate	0.84%
Interest rate per year in excess of Euribor as of date of the notes	1.00%
Equity method investments notes payable with parent company, maturity date	Jan. 31, 2022
Nucor JFE [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment	$ 135,700	71,100
Equity method investment, ownership percentage	50.00%			50.00%
Period used for lag basis, in months	1 month
Facility A [Member] | Duferdofin Nucor S.r.l. [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments credit facilities, amount	$ 183,700			€ 160
Total amount outstanding under equity method investments credit facilities	$ 178,000	$ 146,700		€ 155	€ 122.5
Guarantor obligation percentage of exposure in case of default	50.00%			50.00%
Line of credit facility, maturity period	Apr. 16, 2021

Current Liabilities - Additiona

Current Liabilities - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Liabilities, Current [Abstract]
Book overdrafts	$ 89.8	$ 139.2
Dividends payable, current	$ 123.4	$ 121.8

Debt and Other Financing Arra_3

Debt and Other Financing Arrangements - Schedule of Debt and Other Financing Arrangements (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Apr. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total long-term debt	$ 4,260,600		$ 3,760,600
Less debt issuance costs	27,324	$ 11,900	18,358
Total amounts outstanding	4,233,276		3,742,242
Less current maturities			500,000
Total long-term debt due after one year	4,233,276		3,242,242
Notes, 5.85%, due June 1st, 2018 [Member]
Debt Instrument [Line Items]
Debt instrument face amount			500,000
Notes, 4.125%, due 2022 [Member]
Debt Instrument [Line Items]
Debt instrument face amount	600,000		600,000
Notes, 4.0%, due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument face amount	500,000		500,000
Notes, 3.95%, due 2028 [Member]
Debt Instrument [Line Items]
Debt instrument face amount	500,000	500,000
Notes, 6.40%, due 2037 [Member]
Debt Instrument [Line Items]
Debt instrument face amount	650,000		650,000
Notes, 5.20%, due 2043 [Member]
Debt Instrument [Line Items]
Debt instrument face amount	500,000		500,000
Notes, 4.40%, due 2048 [Member]
Debt Instrument [Line Items]
Debt instrument face amount	500,000	$ 500,000
Industrial Revenue Bonds [Member] | Due from 2020 to 2040 [Member]
Debt Instrument [Line Items]
Debt instrument face amount	$ 1,010,600		$ 1,010,600

Debt and Other Financing Arra_4

Debt and Other Financing Arrangements - Schedule of Debt and Other Financing Arrangements (Parenthetical) (Detail)	Apr. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Due from 2020 to 2040 [Member] | Industrial Revenue Bonds [Member]
Debt Instrument [Line Items]
Debt instrument - maturity year - start		2,020
Debt instrument - maturity year - end		2,040
Due from 2020 to 2040 [Member] | Industrial Revenue Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument interest rate		1.88%	1.65%
Due from 2020 to 2040 [Member] | Industrial Revenue Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument interest rate		2.03%	1.92%
Notes, 5.85%, due June 1st, 2018 [Member]
Debt Instrument [Line Items]
Debt instrument interest rate			5.85%
Debt instrument - maturity year			2,018
Notes, 4.125%, due 2022 [Member]
Debt Instrument [Line Items]
Debt instrument interest rate		4.125%
Debt instrument - maturity year		2,022
Notes, 4.0%, due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument interest rate		4.00%
Debt instrument - maturity year		2,023
Notes, 3.95%, due 2028 [Member]
Debt Instrument [Line Items]
Debt instrument interest rate	3.95%	3.95%
Debt instrument - maturity year	2,028	2,028
Notes, 6.40%, due 2037 [Member]
Debt Instrument [Line Items]
Debt instrument interest rate		6.40%
Debt instrument - maturity year		2,037
Notes, 5.20%, due 2043 [Member]
Debt Instrument [Line Items]
Debt instrument interest rate		5.20%
Debt instrument - maturity year		2,043
Notes, 4.40%, due 2048 [Member]
Debt Instrument [Line Items]
Debt instrument interest rate	4.40%	4.40%
Debt instrument - maturity year	2,048	2,048

Debt and Other Financing Arra_5

Debt and Other Financing Arrangements - Additional Information (Detail) - USD ($)	Apr. 30, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Annual aggregate long-term debt maturities - 2019			$ 0
Annual aggregate long-term debt maturities - 2020			20,000,000
Annual aggregate long-term debt maturities - 2021			0
Annual aggregate long-term debt maturities - 2022			601,000,000
Annual aggregate long-term debt maturities - 2023			500,000,000
Annual aggregate long-term debt maturities - thereafter			3,140,000,000
Net proceeds of debt issuances	$ 986,100,000
Debt issuance costs	11,900,000		$ 27,324,000	$ 18,358,000
Ratio funded debt to total capital			30.00%
Credit facilities, amount outstanding			$ 57,870,000	52,833,000
Notes, 3.95%, due 2028 [Member]
Debt Instrument [Line Items]
Debt instrument face amount	$ 500,000,000		$ 500,000,000
Debt instrument interest rate	3.95%		3.95%
Debt instrument - maturity year	2,028		2,028
Notes, 4.40%, due 2048 [Member]
Debt Instrument [Line Items]
Debt instrument face amount	$ 500,000,000		$ 500,000,000
Debt instrument interest rate	4.40%		4.40%
Debt instrument - maturity year	2,048		2,048
Notes, 5.85%, due June 1st, 2018 [Member]
Debt Instrument [Line Items]
Debt instrument face amount				$ 500,000,000
Debt instrument interest rate				5.85%
Debt instrument - maturity year				2,018
Repayments of debt		$ 500,000,000
Debt instrument - maturity date		Jun. 1, 2018
Harris Steel [Member]
Debt Instrument [Line Items]
Credit facility availability			$ 7,500,000	$ 7,800,000
Credit facilities, amount outstanding			0
Amended and Restated Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility availability		$ 1,500,000,000
Line of revolving credit facility expiration date		2023-04
Ratio on the limit of funded debt to capital on credit facility		60.00%
Credit facilities, amount outstanding			0	0
Letter of Credit [Member]
Debt Instrument [Line Items]
Credit facility availability		$ 100,000,000
Credit facilities, amount outstanding			56,200,000	40,000,000
Letter of Credit [Member] | Nucor Trading S.A. [Member]
Debt Instrument [Line Items]
Credit facilities, amount outstanding			$ 57,900,000	$ 52,800,000
Foreign Currency Loans [Member] | Amended and Restated Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility availability		850,000,000
Revolving Loans For Nucor Subsidiaries [Member] | Amended and Restated Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility availability		500,000,000
Additional Commitments at Nucor's Election in Accordance with Terms of Credit Agreement [Member] | Amended and Restated Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility availability		$ 500,000,000

Capital Stock - Additional Info

Capital Stock - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 06, 2018
Capital Stock [Line Items]
The par value of common stock	$ 0.40
Common stock shares authorized	800,000,000	800,000,000
Preferred stock shares authorized	250,000
Preferred stock par value per share	$ 4
Preferred stock shares issued	0
Preferred stock shares outstanding	0
Dividends declared per share	$ 1.5400	$ 1.5125	$ 1.5025
Repurchase of common stock	$ 853,997,000	$ 90,304,000	$ 5,173,000
Common Stock [Member]
Capital Stock [Line Items]
Share repurchase program available repurchase amount	$ 1,500,000,000
Common Stock [Member] | Maximum [Member]
Capital Stock [Line Items]
Share repurchase program authorized amount				$ 2,000,000,000

Derivative Financial Instrume_3

Derivative Financial Instruments - Fair Values of Derivative Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative Assets, Fair Value	$ 4,772	$ 479
Derivative Liabilities, Fair Value	(8,600)	(8,531)
Derivatives Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities, Fair Value	(8,600)	(4,500)
Derivatives Not Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Fair Value	4,672	479
Commodity Contracts [Member] | Derivatives Designated as Hedging Instrument [Member] | Accrued Expenses and Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities, Fair Value		(2,100)
Commodity Contracts [Member] | Derivatives Designated as Hedging Instrument [Member] | Deferred Credits and Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities, Fair Value	(8,600)	(2,400)
Commodity Contracts [Member] | Derivatives Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Fair Value	100
Commodity Contracts [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Accrued Expenses and Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities, Fair Value		(4,031)
Commodity Contracts [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Fair Value	2,617
Foreign Exchange Contracts [Member] | Derivatives Not Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Fair Value	$ 2,055	$ 479

Derivative Financial Instrume_4

Derivative Financial Instruments - Effect of Derivatives Instruments on Consolidated Statements of Earnings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss), net of tax, Recognized in OCI on Derivatives (Effective Portion)	$ (3,568)	$ (4,523)	$ 2,570
Amount of Gain or (Loss), net of tax, Reclassified from Accumulated OCI into Earnings on Derivatives (Effective Portion)	132	(973)	(9,880)
Derivatives Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	18,181	(15,317)	(3,013)
Cost of Products Sold [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss), net of tax, Reclassified from Accumulated OCI into Earnings on Derivatives (Effective Portion)	132	(973)
Cost of Products Sold [Member] | Commodity Contracts [Member] | Derivatives Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	14,572	(11,973)	(3,251)
Cost of Products Sold [Member] | Commodity Contracts [Member] | Derivatives Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss), net of tax, Recognized in OCI on Derivatives (Effective Portion)	(3,568)	(4,523)	2,570
Amount of Gain or (Loss), net of tax, Reclassified from Accumulated OCI into Earnings on Derivatives (Effective Portion)	132	(973)	(9,880)
Amount of Gain or (Loss) net of tax, Recognized in Earnings on Derivatives (Ineffective Portion)	0	0	0
Cost of Products Sold [Member] | Foreign Exchange Contracts [Member] | Derivatives Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	$ 3,609	$ (3,344)	$ 238

Derivative Financial Instrume_5

Derivative Financial Instruments - Additional Information (Detail) MMBTU in Millions	Dec. 31, 2018MMBTU
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional amount of commodity derivatives	47

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	$ 0	$ 50,000
Derivative contracts	4,772	479
Total assets	17,920,588	15,841,258	$ 15,223,518
Derivative contracts	(8,600)	(8,531)
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	1,084,319	594,946
Short-term investments		50,000
Derivative contracts	4,772	479
Total assets	1,089,091	645,425
Derivative contracts	(8,600)	(8,531)
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	1,084,319	594,946
Short-term investments		50,000
Total assets	1,084,319	644,946
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	4,772	479
Total assets	4,772	479
Derivative contracts	$ (8,600)	$ (8,531)

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair value of short-term and long-term debt, including current maturities	$ 4,450	$ 4,190

Contingencies - Additional Info

Contingencies - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Accrual for environmental loss contingencies, gross	$ 18.4	$ 17.1
Accrued environmental loss contingencies, current	7	3.8
Accrued environmental loss contingencies, noncurrent	$ 11.4	$ 13.3

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesAnniversariesInstallmentshares	Dec. 31, 2017USD ($)$ / shares	Dec. 31, 2016USD ($)$ / shares	May 08, 2014shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercise prices as percentage of the market value on the date of the grant	100.00%
Total intrinsic value of stock options exercised	$ 12.6	$ 4.5	$ 6.8
Total aggregate intrinsic value of stock options	16.8
Total aggregate intrinsic value of stock option exercisable	$ 14.3
Grant date fair value of stock options granted | $ / shares	$ 15.07	$ 12.61	$ 9.12
Compensation expenses for stock options	$ 4.6	$ 8.2	$ 7.8
Omnibus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, common stock available for grant | shares	5,900,000
Omnibus Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, common stock available for grant | shares				13,000,000
Inactive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance | shares	1,900,000
Restricted Stock [Member] | LTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Portion of restricted stock award vesting on anniversary	0.333%
Eligible age of officer for restricted stock award	55 years
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vesting period	3 years
Stock options term, years	10 years
Unrecognized compensation expense related to stock	$ 1.6
Weighted-average recognition period for unrecognized compensation expense related to stock (years)	1 year 8 months 12 days
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock	$ 46.7
Weighted-average recognition period for unrecognized compensation expense related to stock (years)	1 year 8 months 12 days
Number of anniversaries of grant date upon which restricted stock units vest | Anniversaries	3
Installments in which restricted stock units vest and are converted to common stock | Installment	3
Compensation expense	$ 54.3	38	33.9
Total fair value of shares, vested	$ 54.4	39.9	33.4
Restricted Stock Units [Member] | AIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Eligible age of officer for restricted stock award	55 years
Amount of annual incentive award payment participant can elect to defer	50.00%
Additional common stock units for election of deferred annual incentive award, percentage	25.00%
Restricted Stock Awards and Units [Member] | AIP and LTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock	$ 1.6
Weighted-average recognition period for unrecognized compensation expense related to stock (years)	1 year 8 months 12 days
Compensation expense	$ 14.6	17.9	14.8
Total fair value of shares, vested	$ 14.7	$ 9	$ 5.2

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock Option Plans Activity (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding at beginning of year, Shares	4,106	3,591	3,092
Granted, Shares	265	698	899
Exercised, Shares	(543)	(183)	(400)
Canceled, Shares	0	0	0
Outstanding at end of year, Shares	3,828	4,106	3,591
Options exercisable at end of year, Shares	2,112	1,809	1,557
Outstanding at beginning of year, Weighted - Average Exercise Price	$ 47.96	$ 45.32	$ 43.51
Granted, Weighted - Average Exercise Price	65.80	59.07	48.80
Exercised, Weighted - Average Exercise Price	44.33	38.56	39.19
Canceled, Weighted - Average Exercise Price	0	0	0
Outstanding at end of period, Weighted - Average Exercise Price	49.71	47.96	45.32
Options exercisable at end of year, Weighted - Average Exercise Price	$ 45.41	$ 43.39	$ 40.80

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) shares in Thousands	12 Months Ended
	Dec. 31, 2018$ / sharesshares
$35.00 - $45.00 [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Options Outstanding, Number Outstanding | shares	967
Options Outstanding, Weighted-Average Remaining Contractual Life	3 years 8 months 12 days
Options Outstanding, Weighted-Average Exercise Price	$ 40.31
Options Exercisable, Number Exercisable | shares	967
Options Exercisable, Weighted-Average Exercise Price	$ 40.31
$35.00 - $45.00 [Member] | Minimum [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Exercise Price	35
$35.00 - $45.00 [Member] | Maximum [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Exercise Price	$ 45
$45.01 - $55.00 [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Options Outstanding, Number Outstanding | shares	1,897
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 8 months 12 days
Options Outstanding, Weighted-Average Exercise Price	$ 48.81
Options Exercisable, Number Exercisable | shares	1,064
Options Exercisable, Weighted-Average Exercise Price	$ 48.81
$45.01 - $55.00 [Member] | Minimum [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Exercise Price	45.01
$45.01 - $55.00 [Member] | Maximum [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Exercise Price	$ 55
$55.01 - $65.00 [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Options Outstanding, Number Outstanding | shares	698
Options Outstanding, Weighted-Average Remaining Contractual Life	8 years 4 months 24 days
Options Outstanding, Weighted-Average Exercise Price	$ 59.07
Options Exercisable, Number Exercisable | shares	48
Options Exercisable, Weighted-Average Exercise Price	$ 59.07
$55.01 - $65.00 [Member] | Minimum [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Exercise Price	55.01
$55.01 - $65.00 [Member] | Maximum [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Exercise Price	$ 65
$65.01 - $75.00 [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Options Outstanding, Number Outstanding | shares	266
Options Outstanding, Weighted-Average Remaining Contractual Life	9 years 4 months 24 days
Options Outstanding, Weighted-Average Exercise Price	$ 65.80
Options Exercisable, Number Exercisable | shares	33
Options Exercisable, Weighted-Average Exercise Price	$ 65.80
$65.01 - $75.00 [Member] | Minimum [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Exercise Price	65.01
$65.01 - $75.00 [Member] | Maximum [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Exercise Price	$ 75
$35.00 - $75.00 [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Options Outstanding, Number Outstanding | shares	3,828
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 4 months 24 days
Options Outstanding, Weighted-Average Exercise Price	$ 49.71
Options Exercisable, Number Exercisable | shares	2,112
Options Exercisable, Weighted-Average Exercise Price	$ 45.41
$35.00 - $75.00 [Member] | Minimum [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Exercise Price	35
$35.00 - $75.00 [Member] | Maximum [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Exercise Price	$ 75

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Grant Date Fair Value Black-Scholes Option-Pricing Model Assumptions (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Exercise price	$ 65.80	$ 59.07	$ 48.80
Expected dividend yield	2.31%	2.56%	3.07%
Expected stock price volatility	25.28%	26.53%	26.14%
Risk-free interest rate	2.85%	2.02%	1.67%
Expected life (in years)	6 years 6 months	6 years 6 months	6 years 6 months

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Nucor's RSU Activity (Detail) - Restricted Stock Units [Member] - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested at beginning of year, Shares	1,071	1,040	1,031
Granted, Shares	1,013	721	723
Vested, Shares	(827)	(677)	(681)
Canceled, Shares	(11)	(13)	(33)
Unvested at end of year, Shares	1,246	1,071	1,040
Unvested at beginning of year, Grant Date Fair Value	$ 52.62	$ 48.47	$ 47.93
Granted, Grant Date Fair Value	65.80	59.07	48.80
Vested, Grant Date Fair Value	58.98	53.17	48.09
Canceled, Grant Date Fair Value	55.02	50.21	46.44
Unvested at end of year, Grant Date Fair Value	$ 59.09	$ 52.62	$ 48.47

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Nucor's Restricted Stock Activity under AIP and LTIP (Detail) - Restricted Stock Awards and Units [Member] - AIP and LTIP [Member] - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested at beginning of year, Shares	91	67	63
Granted, Shares	256	172	123
Vested, Shares	(217)	(148)	(116)
Canceled, Shares			(3)
Unvested at end of year, Shares	130	91	67
Unvested at beginning of year, Grant Date Fair Value	$ 54.50	$ 45.77	$ 48.07
Granted, Grant Date Fair Value	67.68	60.62	44.03
Vested, Grant Date Fair Value	64.95	51.72	45.16
Canceled, Grant Date Fair Value			45.75
Unvested at end of year, Grant Date Fair Value	$ 62.97	$ 54.50	$ 45.77

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Benefit Plan [Abstract]
Profit Sharing and Retirement Savings Plan, plan expense	$ 307.9	$ 169.4	$ 129
Unfunded obligation	25.5	25.1
Benefit (expense) associated with early retiree medical plan	$ 2.1	$ 2.2	$ 0.6
Discount rate used to calculate benefit obligation	4.24%	3.60%	4.20%
Health care cost trend rate	6.30%	6.60%	6.80%
Projected ultimate future health care cost trend rate	4.50%
Year that trend rate is projected to reach ultimate rate	2,037

Interest Expense (Income) - Sch

Interest Expense (Income) - Schedule of Components of Net Interest Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest Revenue (Expense), Net [Abstract]
Interest expense	$ 161,256	$ 187,282	$ 181,179
Interest income	(25,721)	(13,702)	(11,935)
Interest expense, net	$ 135,535	$ 173,580	$ 169,244

Interest Expense (Income) - Add

Interest Expense (Income) - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest Revenue (Expense), Net [Abstract]
Interest paid	$ 165.7	$ 186.8	$ 183.4

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Sep. 29, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Line Items]
U.S. corporate federal income tax rate				21.00%	35.00%	35.00%
Net tax benefit related to Tax Reform Act			$ 175,200		$ 175,200
Transition tax expense				$ 2,400
Tax expense from revaluation of temporary return to provision adjustment				$ 3,400
Increase in effective tax rate on continuing operations				2.06%
Effective income tax rate				23.17%	21.11%	30.67%
Deferred tax assets write-off		$ 21,800		$ 21,300
Percentage of deferred tax assets write-off, other				0.66%
Domestic manufacturing deduction				(0.00%)	(2.58%)	(2.11%)
Tax Reform Act				0.18%	(10.01%)	0.00%
Non-current deferred tax liabilities included in deferred credits and other liabilities			329,300	$ 332,000	$ 329,300
Non-current deferred tax assets included in other assets			600	700	600
Net federal, state and foreign income taxes paid (refund received)				561,100	699,800	$ 329,300
Current federal and state income taxes receivable			212,500	26,200	212,500
Unrecognized tax benefits			48,845	48,605	48,845	44,088	$ 50,510
Amount of unrecognized tax benefits affects effective tax rate			48,200	48,000	48,200
Estimate of possible decrease in gross uncertain tax positions, exclusive of interest, as a result of the expiration of the statute of limitations				7,400
Expense (benefit) for interest and penalties				(4,000)	(2,200)	$ (2,800)
Accrued interest and penalties related to uncertain tax positions			16,100	11,200	16,100
Foreign Tax Credit Carryforwards [Member]
Income Tax Disclosure [Line Items]
Write off of foreign tax credit carryforward and related valuation allowance due to treasury dept regulations	$ 59,900
Write off of foreign tax credit carryforward and related valuation allowance due to change in tax status of subsidiary		$ 14,500
State and Local Jurisdiction [Member]
Income Tax Disclosure [Line Items]
State net operating loss carryforwards			605,900	483,000	605,900
Foreign Country [Member]
Income Tax Disclosure [Line Items]
Foreign net operating loss carryforwards			$ 28,300	$ 58,600	$ 28,300
Maximum [Member] | State and Local Jurisdiction [Member]
Income Tax Disclosure [Line Items]
Unused net operating loss carryforward expiration year				2,038
Maximum [Member] | Foreign Country [Member]
Income Tax Disclosure [Line Items]
Unused net operating loss carryforward expiration year				2,037
Minimum [Member] | State and Local Jurisdiction [Member]
Income Tax Disclosure [Line Items]
Unused net operating loss carryforward expiration year				2,019
Minimum [Member] | Foreign Country [Member]
Income Tax Disclosure [Line Items]
Unused net operating loss carryforward expiration year				2,029

Income Taxes - Components of Ea

Income Taxes - Components of Earnings (Losses) from Continuing Operations Before Income Taxes and Noncontrolling Interests (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
United States	$ 3,160,111	$ 1,610,652	$ 1,241,117
Foreign	69,280	139,305	57,542
Earnings before income taxes and noncontrolling interests	$ 3,229,391	$ 1,749,957	$ 1,298,659

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal, current	$ 633,868	$ 504,865	$ 286,224
State, current	96,622	37,308	27,353
Foreign, current	14,800	48,386	13,211
Total current	745,290	590,559	326,788
Federal, deferred	4,953	(207,006)	71,777
State, deferred	6,847	(4,533)	5,193
Foreign, deferred	(8,783)	(9,634)	(5,515)
Total deferred	3,017	(221,173)	71,455
Total provision for income taxes	$ 748,307	$ 369,386	$ 398,243

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the Federal Statutory Tax Rate to Total Provisions (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Taxes computed at statutory rate	21.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit	2.52%	1.22%	1.67%
Federal research credit	(0.14%)	(0.24%)	(0.28%)
Domestic manufacturing deduction	(0.00%)	(2.58%)	(2.11%)
Equity in losses of foreign joint venture	0.08%	0.13%	0.27%
Foreign rate differential	(0.07%)	(0.62%)	(1.05%)
Noncontrolling interests	(0.78%)	(1.24%)	(2.81%)
Tax Reform Act	0.18%	(10.01%)	0.00%
Out-of-period correction	(0.00%)	(0.00%)	(0.22%)
Other, net	0.38%	(0.55%)	0.20%
Provision for income taxes	23.17%	21.11%	30.67%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Components of Deferred Tax Assets and Liabilities [Abstract]
Accrued liabilities and reserves	$ 128,553	$ 127,955
Allowance for doubtful accounts	20,134	15,136
Inventory	63,950	61,522
Post-retirement benefits	8,746	9,167
Commodity hedges	1,393	2,056
Net operating loss carryforward	27,131	19,895
Tax credit carryforwards	16,792	92,380
Other deferred tax assets	779
Valuation allowance	(30,104)	(96,107)
Total deferred tax assets	237,374	232,004
Holdbacks and amounts not due under contracts	(10,731)	(10,214)
Intangibles	(167,374)	(164,716)
Property, plant and equipment	(390,575)	(385,815)
Total deferred tax liabilities	(568,680)	(560,745)
Total net deferred tax liabilities	$ (331,306)	$ (328,741)

Income Taxes - Reconciliation_2

Income Taxes - Reconciliation of the Beginning and Ending Amounts of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 48,845	$ 44,088	$ 50,510
Additions based on tax positions related to current year	16,424	11,154	6,157
Reductions based on tax positions related to current year	0	0	0
Additions based on tax positions related to prior years	199	2,556	147
Reductions based on tax positions related to prior years	(8,198)	(5,461)	(8,201)
Reductions due to settlements with taxing authorities	(2,160)		(258)
Reductions due to statute of limitations lapse	(6,505)	(3,492)	(4,267)
Balance at end of year	$ 48,605	$ 48,845	$ 44,088

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning Balance, Gains and Losses on Hedging Derivatives	$ (2,800)	$ 750
Other comprehensive income (loss) before reclassifications, Gains and Losses on Hedging Derivatives	(3,568)	(4,523)	$ 2,570
Amounts reclassified from accumulated other comprehensive (loss) income into earnings, Gains and Losses on Hedging Derivatives	(132)	973	9,880
Net current-period other comprehensive income (loss), Gains and Losses on Hedging Derivatives	(3,700)	(3,550)
Ending Balance, Gains and Losses on Hedging Derivatives	(6,500)	(2,800)	750
Beginning Balance, Foreign Currency Gains (Losses)	(257,513)	(326,170)
Other comprehensive income (loss) before reclassifications, Foreign Currency Gains (Losses)	(47,133)	68,657	25,495
Amounts reclassified from accumulated other comprehensive income (loss) into earnings, Foreign Currency Gains (Losses)	0	0
Net current-period other comprehensive income (loss), Foreign Currency Gains (Losses)	(47,133)	68,657
Ending Balance, Foreign Currency Gains (Losses)	(304,646)	(257,513)	(326,170)
Beginning Balance, Adjustment to Early Retiree Medical Plan	5,632	7,577
Other comprehensive income (loss) before reclassifications, Adjustment to Early Retiree Medical Plan	1,731	(1,530)	(3,589)
Amounts reclassified from accumulated other comprehensive (loss) income into earnings, Adjustment to Early Retiree Medical Plan	(350)	(415)	(837)
Net current-period other comprehensive income (loss), Adjustment to Early Retiree Medical Plan	1,381	(1,945)
Ending Balance, Adjustment to Early Retiree Medical Plan	7,013	5,632	7,577
Beginning Balance	(254,681)	(317,843)
Other comprehensive income (loss) before reclassifications	(48,970)	62,604
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	(482)	558
Net current-period other comprehensive income (loss)	(49,452)	63,162	33,519
Ending Balance	$ (304,133)	$ (254,681)	$ (317,843)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive (loss) income into earnings, Gains and Losses on Hedging Derivatives	$ (132)	$ 973	$ 9,880
Amounts reclassified from accumulated other comprehensive (loss) income into earnings, Adjustment to Early Retiree Medical Plan	(350)	(415)	(837)
AOCI reclassification impact on tax	0	400	5,800
AOCI reclassification impact on tax	(108)	(279)	$ (309)
Cost of Products Sold [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive (loss) income into earnings, Gains and Losses on Hedging Derivatives	(132)	973
Amounts reclassified from accumulated other comprehensive (loss) income into earnings, Adjustment to Early Retiree Medical Plan	(350)	(415)
AOCI reclassification impact on tax	0	400
AOCI reclassification impact on tax	$ (108)	$ (279)

Earnings Per Share - Computatio

Earnings Per Share - Computations of Basic and Diluted Net Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Basic net earnings	$ 646,779	$ 676,656	$ 683,153	$ 354,179	$ 383,891	$ 254,850	$ 323,048	$ 356,899	$ 2,360,767	$ 1,318,688	$ 796,271
Earnings allocated to participating securities, Basic									(9,344)	(4,549)	(2,632)
Net earnings available to common stockholders, Basic									$ 2,351,423	$ 1,314,139	$ 793,639
Average shares outstanding									315,858	319,990	319,563
Basic net earnings per share	$ 2.08	$ 2.13	$ 2.14	$ 1.11	$ 1.20	$ 0.79	$ 1	$ 1.11	$ 7.44	$ 4.11	$ 2.48
Diluted net earnings	$ 646,779	$ 676,656	$ 683,153	$ 354,179	$ 383,891	$ 254,850	$ 323,048	$ 356,899	$ 2,360,767	$ 1,318,688	$ 796,271
Earnings allocated to participating securities, Diluted									(9,317)	(4,539)	(2,631)
Net earnings available to common stockholders, Diluted									$ 2,351,450	$ 1,314,149	$ 793,640
Basic shares outstanding									315,858	319,990	319,563
Dilutive effect of stock options and other									875	783	259
Diluted average shares outstanding									316,733	320,773	319,822
Diluted net earnings per share	$ 2.07	$ 2.13	$ 2.13	$ 1.10	$ 1.20	$ 0.79	$ 1	$ 1.11	$ 7.42	$ 4.10	$ 2.48

Earnings Per Share - Anti-dilut

Earnings Per Share - Anti-dilutive Stock Options (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Weighted-average shares	156	407	942
Weighted-average exercise price	$ 65.80	$ 59.07	$ 47.04

Segments - Additional Informati

Segments - Additional Information (Detail)	3 Months Ended
	Oct. 01, 2016
Hunter Ridge Energy Services LLC [Member]
Segment Reporting Information [Line Items]
Equity method investment ownership percentage, percentage of investee's ownership interest sold	50.00%

Segments - Segments (Detail)

Segments - Segments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net sales	$ 6,295,884	$ 6,742,202	$ 6,460,774	$ 5,568,419	$ 5,092,328	$ 5,170,117	$ 5,174,769	$ 4,815,179	$ 25,067,279	$ 20,252,393	$ 16,208,122
Depreciation expense									630,879	635,833	613,192
Amortization expense									88,758	91,228	73,862
Earnings (loss) before income taxes and noncontrolling interests									3,229,391	1,749,957	1,298,659
Total assets	17,920,588				15,841,258				17,920,588	15,841,258	15,223,518
Capital expenditures									997,256	507,074	617,677
Operating Segments [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales									16,245,218	12,929,709	10,546,847
Depreciation expense									378,146	377,210	368,859
Amortization expense									9,400	9,706	7,632
Earnings (loss) before income taxes and noncontrolling interests									3,500,085	1,953,075	1,680,156
Total assets	9,244,086				7,671,217				9,244,086	7,671,217	6,980,979
Capital expenditures									720,310	336,760	357,545
Operating Segments [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales									6,796,501	5,579,744	4,452,649
Depreciation expense									80,681	76,992	45,674
Amortization expense									51,997	52,597	36,845
Earnings (loss) before income taxes and noncontrolling interests									467,105	337,978	294,039
Total assets	4,734,636				4,323,907				4,734,636	4,323,907	3,651,118
Capital expenditures									88,585	90,952	49,149
Operating Segments [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales									2,025,560	1,742,940	1,208,626
Depreciation expense									161,666	172,699	191,466
Amortization expense									27,361	28,925	29,385
Earnings (loss) before income taxes and noncontrolling interests									236,241	129,296	(95,121)
Total assets	3,492,126				3,396,110				3,492,126	3,396,110	3,235,237
Capital expenditures									169,926	59,036	194,112
Intercompany Eliminations [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales									3,924,160	2,916,017	2,066,547
Intercompany Eliminations [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales									207,003	118,249	110,368
Intercompany Eliminations [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales									11,460,645	9,191,081	5,997,498
Corporate and Eliminations Items [Member]
Segment Reporting Information [Line Items]
Net sales									(15,591,808)	(12,225,347)	(8,174,413)
Earnings (loss) before income taxes and noncontrolling interests									(974,040)	(670,392)	(580,415)
Total assets	$ 449,740				$ 450,024				449,740	450,024	1,356,184
Corporate [Member]
Segment Reporting Information [Line Items]
Depreciation expense									10,386	8,932	7,193
Capital expenditures									$ 18,435	$ 20,326	$ 16,871

Segments - Schedule of Net Sale

Segments - Schedule of Net Sale by Product to External Customers (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net sales to external customers	$ 6,295,884	$ 6,742,202	$ 6,460,774	$ 5,568,419	$ 5,092,328	$ 5,170,117	$ 5,174,769	$ 4,815,179	$ 25,067,279	$ 20,252,393	$ 16,208,122
Sheet [Member]
Segment Reporting Information [Line Items]
Net sales to external customers									7,571,765	6,407,974	5,178,467
Bar [Member]
Segment Reporting Information [Line Items]
Net sales to external customers									4,709,292	3,558,806	2,886,648
Structural [Member]
Segment Reporting Information [Line Items]
Net sales to external customers									1,830,476	1,317,995	1,277,547
Plate [Member]
Segment Reporting Information [Line Items]
Net sales to external customers									2,133,685	1,644,934	1,204,185
Tubular Products [Member]
Segment Reporting Information [Line Items]
Net sales to external customers									1,347,577	917,235	60,106
Rebar Fabrication [Member]
Segment Reporting Information [Line Items]
Net sales to external customers									1,496,194	1,306,418	1,272,338
Other Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales to external customers									3,952,730	3,356,091	3,120,205
Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales to external customers									$ 2,025,560	$ 1,742,940	$ 1,208,626

Revenue - Additional Informatio

Revenue - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customers [Line Items]
Contract with customer, timing of satisfaction of performance obligation and payment	The durations of Nucor's contracts with customers are generally one year or less. Customer payment terms are generally 30 days.
Contract liabilities	$ 91.2	$ 72.3
Revenue reclassified from contract liabilities	$ 61.3
Steel Mills [Member]
Revenue from Contract with Customers [Line Items]
Contract with customer, timing of satisfaction of performance obligation and payment	One year or less

Revenue - Schedule of Net Sales

Revenue - Schedule of Net Sales Disaggregates by Major Source (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Revenue from Contract with Customers [Line Items]
Revenues	$ 25,067,279
Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	7,571,765
Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	4,709,292
Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,830,476
Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,133,685
Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,347,577
Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,496,194
Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	3,952,730
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,025,560
Steel Mills [Member]
Revenue from Contract with Customers [Line Items]
Revenues	16,245,218
Steel Mills [Member] | Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	7,571,765
Steel Mills [Member] | Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	4,709,292
Steel Mills [Member] | Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,830,476
Steel Mills [Member] | Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,133,685
Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	6,796,501
Steel Products [Member] | Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,347,577
Steel Products [Member] | Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,496,194
Steel Products [Member] | Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	3,952,730
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,025,560
Raw Materials [Member] | Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	$ 2,025,560

Quarterly Information - Schedul

Quarterly Information - Schedule of Quarterly Information (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 6,295,884	$ 6,742,202	$ 6,460,774	$ 5,568,419	$ 5,092,328	$ 5,170,117	$ 5,174,769	$ 4,815,179	$ 25,067,279	$ 20,252,393	$ 16,208,122
Gross margin	1,112,262	1,290,150	1,166,590	726,406	520,568	578,964	709,625	760,250
Net earnings	681,070	706,287	713,615	380,112	395,094	266,105	341,724	377,648	2,481,084	1,380,571	900,416
Net earnings attributable to Nucor stockholders	$ 646,779	$ 676,656	$ 683,153	$ 354,179	$ 383,891	$ 254,850	$ 323,048	$ 356,899	$ 2,360,767	$ 1,318,688	$ 796,271
Basic	$ 2.08	$ 2.13	$ 2.14	$ 1.11	$ 1.20	$ 0.79	$ 1	$ 1.11	$ 7.44	$ 4.11	$ 2.48
Diluted	$ 2.07	$ 2.13	$ 2.13	$ 1.10	$ 1.20	$ 0.79	$ 1	$ 1.11	$ 7.42	$ 4.10	$ 2.48

Quarterly Information - Sched_2

Quarterly Information - Schedule of Quarterly Information (Unaudited) (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended						12 Months Ended
	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information [Line Items]
Tax benefit related to insurance recoveries	$ 18,000	$ 9,600
Deferred tax assets write-off			$ 21,800				$ 21,300
Tax benefit included in gross margin related to insurance recoveries	24,800	$ 23,300
Impairment of assets							$ 110,000
Net benefit related to tax return true-ups and state tax credits					$ 13,200
Expense related to certain legal matters					$ 22,500
Net tax benefit related to Tax Reform Act				$ 175,200				$ 175,200
Proved Producing Natural Gas Well Assets [Member]
Quarterly Financial Information [Line Items]
Impairment of assets	$ 110,000
Southland & Republic [Member]
Quarterly Financial Information [Line Items]
Inventory-related purchase accounting charges						$ 9,800