Supplemental Balance Sheet, Income Statement and Cash Flow Information - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accrued liabilities
Accrued compensation	$ 82,462	$ 97,003
Deferred revenue and proceeds on insurance and asset sales	61,473	89,051
Other taxes payable	28,602	31,472
Workers' compensation liabilities	7,788	30,214
Interest payable	62,935	51,316
Litigation reserves	13,976	14,736
Dividends declared and payable	3,653	7,832
Other accrued liabilities	15,196	11,658
Accrued liabilities	$ 276,085	$ 333,282