Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Restricted cash	$ 4,674	$ 3,838
Prepaid vehicle licenses	62,772	50,343
Prepaid operating taxes	14,320	20,242
Prepaid sales commission	12,988	9,731
Prepaid insurance	15,688	12,074
Start-up costs	8,001	5,284
Other	41,040	39,768
Total	$ 159,483	$ 141,280