Commitments and Contingencies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Current portion of performance guarantee obligations	$ 3,885	$ 3,885	$ 2,580
Letter of credit outstanding	725	725	725
Other commitment	32,400	32,400
Payments for dealer commitments	9,700	31,700
Dealer commitment, maximum annual payments, 2020	26,300	26,300
Dealer commitment, maximum annual payments, 2021	24,200	24,200
Dealer commitment, maximum annual payments, 2022	25,200	25,200
Dealer commitment, maximum annual payments, 2023	1,000	1,000
Purchase commitment, remaining minimum amount committed	6,100	6,100
Purchase commitment, remaining minimum amount committed, 2020	25,200	25,200
Purchase commitment, remaining minimum amount committed, 2021	27,400	27,400
Purchase commitment, remaining minimum amount committed, 2022	27,200	27,200
Purchase commitment, remaining minimum amount committed, 2023	27,100	27,100
Purchase commitment, remaining minimum amount committed, 2024	20,200	20,200
Performance Guarantee Obligations
Loss Contingencies [Line Items]
Performance guarantee obligations	5,675	5,675	6,044	$ 5,440	$ 4,173
Current portion of performance guarantee obligations	3,900	3,900	2,600
Long-term portion of performance guarantee obligations	$ 1,800	$ 1,800	$ 3,500