Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Insurance and claims accruals	$ 48,537	$ 47,031
Compensation - related accruals	8,067	7,413
Allowance for uncollectible accounts	3,690	3,628
Other	1,863	1,896
Gross deferred income tax assets	62,157	59,968
Property and equipment	305,575	287,061
Prepaid expenses	4,928	4,772
Other	1,323	1,585
Gross deferred income tax liabilities	311,826	293,418
Net deferred income tax liability	$ 249,669	$ 233,450