Debt and Other Financing Arrangements (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Schedule of Debt and Other Financing Arrangements

	(in thousands)
December 31,	2020		2019
Industrial revenue bonds due from 2022 to 2040*	$	1,153,240	$	1,010,600
Notes, 4.125%, due 2022		600,000		600,000
Notes, 4.000%, due 2023		500,000		500,000
Notes, 2.000%, due 2025		500,000		—
Notes, 3.950%, due 2028		500,000		500,000
Notes, 2.700%, due 2030		500,000		—
Notes, 6.400%, due 2037		543,331		650,000
Notes, 5.200%, due 2043		338,133		500,000
Notes, 4.400%, due 2048		329,219		500,000
Notes, 2.979%, due 2055		439,317		—
Finance lease obligations		90,338		85,224
Total long-term debt and finance lease obligations		5,493,578		4,345,824
Less premium on debt exchange		180,045		—
Less debt issuance costs		30,859		25,259
Total amounts outstanding		5,282,674		4,320,565
Less current maturities of long-term debt		—		20,000
Less current portion of finance lease obligations		10,885		9,264
Total long-term debt and finance lease obligations due after    one year	$	5,271,789	$	4,291,301

* The industrial revenue bonds had variable rates ranging from 0.16% to 0.19% at December 31, 2020 and 1.61% to 1.82% at December 31, 2019.