Fair Value - Estimated Fair Values and Carrying Values for Customer Receivables and Debt Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Jul. 31, 2014
Customer financing receivables | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer financing receivables	$ 54,616	$ 55,855
Customer financing receivables | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer financing receivables	43,567	44,002
LIBOR 4% term loan due November 2020 | Term loan | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	1,117	1,536
LIBOR 4% term loan due November 2020 | Term loan | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 1,116	1,590
10% convertible promissory Constellation note due December 2021 | Convertible promissory notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	10.00%
10% convertible promissory Constellation note due December 2021 | Convertible promissory notes | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 40,709	36,482
10% convertible promissory Constellation note due December 2021 | Convertible promissory notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 40,709	32,070
10% convertible promissory notes due December 2021 | Convertible promissory notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	10.00%
10% convertible promissory notes due December 2021 | Convertible promissory notes | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 338,944	273,410
10% convertible promissory notes due December 2021 | Convertible promissory notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 340,694	$ 302,047
Notes due July 2024, Recourse | Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	10.00%	10.00%
Notes due July 2024, Recourse | Notes | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 83,230	$ 89,962
Notes due July 2024, Recourse | Notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 72,582	$ 97,512
7.5% term loan due September 2028 | Term loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	7.50%	7.50%
7.5% term loan due September 2028 | Term loan | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 33,036	$ 34,969
7.5% term loan due September 2028 | Term loan | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 32,053	41,108
6.07% senior secured notes due March 2030 | Senior secured notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	6.10%
6.07% senior secured notes due March 2030 | Senior secured notes | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 79,319	80,016
6.07% senior secured notes due March 2030 | Senior secured notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	78,831	87,618
LIBOR 2.5% term loan due December 2021 | Term loan | Net Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	119,646	120,436
LIBOR 2.5% term loan due December 2021 | Term loan | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument	$ 104,377	$ 120,510
LIBOR | LIBOR 4% term loan due November 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
LIBOR margin (as a percentage)	4.00%
LIBOR | LIBOR 4% term loan due November 2020 | Term loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
LIBOR margin (as a percentage)	4.00%
LIBOR | LIBOR 2.5% term loan due December 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
LIBOR margin (as a percentage)	2.50%
LIBOR | LIBOR 2.5% term loan due December 2021 | Term loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
LIBOR margin (as a percentage)	2.50%
PPA IV | 6.07% senior secured notes due March 2030 | Senior secured notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage	6.07%	6.10%	6.07%