Fair Value - Estimated Fair Values and Carrying Values for Customer Receivables and Debt Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Senior secured notes | Senior Secured Notes due March 2025, Non-Recourse | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 84,191	$ 89,564
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	87,275	95,114
Senior secured notes | Senior Secured Notes due March 2030, Non-Recourse | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	83,223	84,032
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	88,781	93,264
Term loan | Term Loan due September 2028, Non-Recourse | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	36,684	36,940
Term loan | Term Loan due September 2028, Non-Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	44,599	46,713
Term loan | Senior Secured Notes due October 2020, Non-Recourse | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	24,133	24,364
Term loan | Senior Secured Notes due October 2020, Non-Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	26,797	27,206
Term loan | Term Loan due December 2021, Non-Recourse | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	124,526	125,596
Term loan | Term Loan due December 2021, Non-Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	130,025	131,817
Term loan | Term Loan due November 2020, Recourse | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	4,050	4,888
Term loan | Term Loan due November 2020, Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	4,265	5,148
Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	254,120	244,717
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	98,486	211,000
Convertible promissory notes | Convertible Promissory Notes One due December 2020 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	290,382	377,496
Convertible promissory notes | Convertible Promissory Notes One due December 2020 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	360,565	359,865
Notes | Notes due July 2024, Recourse | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	95,140	94,517
Notes | Notes due July 2024, Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	101,953	106,124
Customer financing receivables | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer financing receivables	75,361	77,885
Customer financing receivables | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer financing receivables	$ 52,517	$ 55,255