Accrued Liabilities Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Liabilities [Abstract]
Accrued insurance costs	$ 104,557	$ 109,505
Accrued compensation	38,547	55,789
Deferred revenue	52,589	53,348
Taxes other than income	28,397	27,711
Income taxes payable	0	26,797
Accrued legal settlement	440	11,000
Deferred compensation	9,711	8,687
Accrued interest payable	1,391	5,643
Deferred rent	0	3,503
Accrued dividends	15,912	0
Accrued other	24,233	35,476
Accrued liabilities	$ 275,777	$ 337,459