Supplemental Balance Sheet and Income Statement Information - Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accrued liabilities
Accrued compensation	$ 85,811	$ 92,358
Deferred revenue and proceeds on insurance and asset sales	104,600	149,266
Other taxes payable	17,196	33,199
Workers' compensation liabilities	15,214	16,316
Interest payable	53,728	59,718
Litigation reserves	18,890	24,926
Current liability to discontinued operations		2,445
Dividends declared and payable	7,832	25,330
Other accrued liabilities	16,492	14,354
Accrued liabilities	$ 319,763	$ 417,912