Supplemental Balance Sheet and Income Statement Information - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued liabilities
Accrued compensation	$ 92,358	$ 130,970
Deferred revenue	116,700	218,400
Deferred revenue and proceeds on insurance and asset sales	149,266	218,370
Other taxes payable	33,199	32,095
Workers' compensation liabilities	16,316	13,987
Interest payable	59,718	65,642
Litigation reserves	24,926	18,830
Current liability to discontinued operations	2,445	6,074
Dividends declared and payable	25,330	17,148
Other accrued liabilities	14,354	29,928
Accrued liabilities	$ 417,912	$ 533,044