Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Accrued insurance	$ 31,100	$ 28,600
Operating loss carryforwards and tax credits	82,100	70,500
Compensation and benefits	32,800	16,800
Bad debt	3,700	900
Other	12,300	11,500
Valuation allowance	(45,800)	(48,800)
Total deferred tax assets	116,200	79,500
Deferred tax liabilities:
Property and equipment	205,000	179,500
Goodwill	58,700	49,600
Other intangible assets	30,700	35,000
Gain on remeasurement of equity investee	7,000	7,000
Revenue recognition	22,400	20,600
Investments in unconsolidated entities	79,800	74,000
Other	15,500	10,100
Total deferred tax liabilities	419,100	375,800
Net deferred tax liabilities	$ (302,938)	$ (296,326)