Fair Value - Estimated Fair Values and Carrying Values for Customer Receivables and Debt Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 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 | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 75,786	$ 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	79,341	80,838
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	81,806	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	88,715	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	2,795	3,214
Term loan | Term Loan due November 2020, Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	2,914	3,311
Term loan | Term Loan due September 2028, Non-Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	35,758	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	41,759	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	23,734	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	25,679	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	122,701	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	$ 125,770	123,040
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]
Interest rate percentage	5.00%
Debt Instrument	$ 35,136	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	33,832	31,546
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	267,289	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	418,999	353,368
Notes | Notes due July 2024, Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	96,073	95,555
Notes | Notes due July 2024, Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	99,598	99,260
Customer financing receivables | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer financing receivables	71,337	72,676
Customer financing receivables | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer financing receivables	$ 51,312	$ 51,541
Affiliated entity | Term Loan due November 2020, Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	4.00%
Affiliated entity | Senior Secured Notes due October 2020, Non-Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	5.25%
Affiliated entity | Term Loan due December 2021, Non-Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	2.50%
Affiliated entity | 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]
Interest rate percentage	6.00%
PPA Company II | 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%
PPA Company IIIa | Term loan | Term Loan due September 2028, Non-Recourse
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	7.50%
PPA Company IV | 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%