Debt and Other Financing Arrangements (Tables)

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

Schedule of Debt and Other Financing Arrangements

	(in thousands) December 31,
	2016		2015
Industrial revenue bonds:
0.30% to 1.00%, variable, due from 2020 to 2040	$	1,010,600	$	1,010,600
Notes, 5.75%, due 2017		600,000		600,000
Notes, 5.85%, due 2018		500,000		500,000
Notes, 4.125%, due 2022		600,000		600,000
Notes, 4.0%, due 2023		500,000		500,000
Notes, 6.40%, due 2037		650,000		650,000
Notes, 5.20%, due 2043		500,000		500,000
Total long-term debt		4,360,600		4,360,600
Less debt issuance costs		21,459		23,455
Total amounts outstanding		4,339,141		4,337,145
Less current maturities		600,000		—
Total long-term debt due after one year	$	3,739,141	$	4,337,145