Fair Value - Estimated Fair Values and Carrying Values for Customer Receivables and Debt Instruments (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Notes due July 2024, Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	10.00%
Senior secured notes | Senior Secured Notes due March 2025, Non-Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	5.22%
Senior secured notes | Senior Secured Notes due March 2025, Non-Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 0	$ 78,566
Senior secured notes | Senior Secured Notes due March 2025, Non-Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 0	80,838
Senior secured notes | Senior Secured Notes due March 2030, Non-Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	6.07%
Senior secured notes | Senior Secured Notes due March 2030, Non-Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 80,677	82,337
Senior secured notes | Senior Secured Notes due March 2030, Non-Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	88,243	85,917
Term loan | Term Loan due November 2020, Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	1,956	3,214
Term loan | Term Loan due November 2020, Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 2,016	3,311
Term loan | Term Loan due September 2028, Non-Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	7.50%
Term loan | Term Loan due September 2028, Non-Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 35,281	36,319
Term loan | Term Loan due September 2028, Non-Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	41,335	39,892
Term loan | Senior Secured Notes due October 2020, Non-Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	23,571	23,916
Term loan | Senior Secured Notes due October 2020, Non-Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	24,637	25,441
Term loan | Term Loan due December 2021, Non-Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	121,069	123,384
Term loan | Term Loan due December 2021, Non-Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 121,417	123,040
Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	5.00%
Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 36,026	34,706
Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 34,509	31,546
Convertible promissory notes | Convertible Promissory Notes One due December 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	6.00%
Convertible promissory notes | Convertible Promissory Notes One due December 2020 | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 275,716	263,284
Convertible promissory notes | Convertible Promissory Notes One due December 2020 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	289,887	353,368
Notes | Notes due July 2024, Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	89,673	95,555
Notes | Notes due July 2024, Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	94,974	99,260
Customer financing receivables | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer financing receivables	68,535	72,676
Customer financing receivables | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer financing receivables	$ 52,495	$ 51,541
LIBOR | Term Loan due November 2020, Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
LIBOR margin (as a percentage)	4.00%
LIBOR | Senior Secured Notes due October 2020, Non-Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
LIBOR margin (as a percentage)	5.25%
LIBOR | Term Loan due December 2021, Non-Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
LIBOR margin (as a percentage)	2.50%