Fair Value - Estimated Fair Values and Carrying Values for Customer Receivables and Debt Instruments (Details) - USD ($) $ in Thousands	Jun. 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 | 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 | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	81,223	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	90,136	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	2,376	3,214
Term loan | Term Loan due November 2020, Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	2,458	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	35,532	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	41,368	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	23,661	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	25,028	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	121,952	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	$ 123,046	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	$ 35,576	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	33,524	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	271,503	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	393,395	353,368
Notes | Notes due July 2024, Recourse | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	96,384	95,555
Notes | Notes due July 2024, Recourse | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	96,859	99,260
Customer financing receivables | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer financing receivables	69,963	72,676
Customer financing receivables | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer financing receivables	$ 52,517	$ 51,541
PPA 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 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 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%
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 One due December 2020 | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	6.00%