Income Taxes - Analysis of Deferred Tax Assets and Deferred Tax Liabilities Showing Tax Effects of Significant Temporary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets
Property and leasehold costs	$ 241,833	$ 95,141
Liabilities for dismantlements	37,728	28,475
Postretirement and other employee benefits	114,790	128,281
U. S. net operating loss	577,531	589,067
Investment in partnership	39,396	65,216
Other deferred tax assets	135,838	112,685
Total gross deferred tax assets	1,147,116	1,018,865
Less valuation allowance	(111,259)	(106,448)
Net deferred tax assets	1,035,857	912,417
Deferred tax liabilities
Deferred tax on undistributed foreign earnings	(5,000)	(5,000)
Accumulated depreciation, depletion and amortization	(786,846)	(665,255)
Other deferred tax liabilities	(41,387)	(27,250)
Total gross deferred tax liabilities	(833,233)	(697,505)
Net deferred tax (liabilities) assets	$ 202,624	$ 214,912