Leases - Operating Leases - Vehicle Fleet Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 30, 2018
Operating leases
Restricted cash, current	$ 1,735	$ 1,250
Operating lease cost	2,530	16,452
Vehicles, 2018 Vehicle Leases
Operating leases
Operating lease, term				12 months
Operating lease, renewal term				1 month
Restricted cash, current	1,300	1,300
Operating lease cost	$ 1,400	$ 1,500
Rent expenses			$ 800