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.