Outstanding Loans and Security Agreements - Recourse Debt Facilities (Additional Information) (Details)					1 Months Ended			3 Months Ended			9 Months Ended
	Oct. 08, 2020 USD ($)	Jun. 18, 2020 USD ($) shares $ / shares	May 01, 2020 USD ($)	Mar. 31, 2020 USD ($) $ / shares	Oct. 31, 2020 shares	Aug. 31, 2020 USD ($) $ / shares	Nov. 30, 2019 $ / shares shares	Sep. 30, 2020 USD ($) $ / shares	Mar. 31, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Oct. 07, 2020 USD ($)	Oct. 01, 2020 USD ($)	Jun. 30, 2020 USD ($) $ / shares	Mar. 30, 2020 $ / shares	Dec. 31, 2019 USD ($)	Jul. 01, 2017
Debt Instrument [Line Items]
Unpaid Principal Balance								$ 707,239,000			$ 707,239,000						$ 658,083,000
Debt make-whole expense												$ 5,934,000
Long-term debt carrying value								570,347,000			570,347,000						636,812,000
Gain (loss) on extinguishment of debt								(1,220,000)		$ 0	12,878,000	0
Payments of debt issuance costs											13,247,000	0
Current portion of debt								129,657,000			129,657,000						337,583,000
Long-term portion of debt								440,690,000			440,690,000						299,229,000
Interest expense								20,300,000		22,900,000	57,500,000	70,700,000
Amortization of debt issuance costs												16,295,000
Contractual interest expense								$ 19,902,000		$ 21,323,000	$ 55,030,000	$ 65,845,000
Subsequent Event
Debt Instrument [Line Items]
Debt instrument, unamortized premium													$ 3,200,000
10.25% senior secured notes due March 2027
Debt Instrument [Line Items]
Interest rate percentage			10.25%
Redemption price, percentage											101.00%
Convertible promissory notes | Convertible Promissory Notes Interest Rate 5% Due December 2020, Recourse
Debt Instrument [Line Items]
Unpaid Principal Balance																	$ 33,104,000
Interest rate percentage				10.00%				5.00%	10.00%		5.00%					5.00%	5.00%
Convertible stock price (in dollars per share) | $ / shares				$ 8.00					$ 8.00							$ 38.64
Debt make-whole expense									$ 3,800,000
Long-term debt carrying value																	$ 36,482,000
Current portion of debt																	36,482,000
Long-term portion of debt																	0
Convertible promissory notes | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse
Debt Instrument [Line Items]
Unpaid Principal Balance																	$ 289,299,000
Interest rate percentage																	6.00%
Convertible stock price (in dollars per share) | $ / shares							$ 11.25
Long-term debt carrying value																	$ 273,410,000
Debt conversion, shares issued (in shares) | shares							616,302
Current portion of debt																	273,410,000
Long-term portion of debt																	0
Convertible promissory notes | 10% convertible promissory notes due December 20211
Debt Instrument [Line Items]
Interest rate percentage								10.00%			10.00%
Current portion of debt								$ 99,379,000			$ 99,379,000
Long-term portion of debt								0			0
Convertible promissory notes | Convertible Promissory Notes Interest Rate 10% Due December 2021
Debt Instrument [Line Items]
Convertible stock price (in dollars per share) | $ / shares				$ 8.00					$ 8.00
Debt face amount				$ 290,000,000.0					$ 290,000,000.0
Repayments of convertible debt			$ 70,000,000.0
Convertible promissory notes | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse, Amendment
Debt Instrument [Line Items]
Interest rate percentage				10.00%					10.00%							6.00%
Convertible stock price (in dollars per share) | $ / shares				$ 8.00					$ 8.00							$ 11.25
Convertible, number of equity instruments (in shares) | shares		4,700,000
Debt instrument, unamortized premium		$ 3,400,000
Notes | 10% notes due July 2024
Debt Instrument [Line Items]
Unpaid Principal Balance								$ 79,000,000			$ 79,000,000						$ 93,000,000
Interest rate percentage								10.00%			10.00%						10.00%
Long-term debt carrying value								$ 76,743,000			$ 76,743,000						$ 89,962,000
Accrued and unpaid interest								1,300,000			1,300,000						3,900,000
Current portion of debt								16,000,000			16,000,000						14,000,000
Long-term portion of debt								60,743,000			60,743,000						75,962,000
Notes | 10.25% senior secured notes due March 2027
Debt Instrument [Line Items]
Unpaid Principal Balance								$ 70,000,000.0			$ 70,000,000.0
Interest rate percentage								10.25%			10.25%
Long-term debt carrying value								$ 68,526,000			$ 68,526,000
Debt face amount			70,000,000.0
Current portion of debt								0			0
Long-term portion of debt								68,526,000			68,526,000
Convertible debt | Convertible Promissory Notes Interest Rate 5% Due December 2020, Recourse
Debt Instrument [Line Items]
Extinguishment of debt amount				$ 33,100,000
Debt make-whole expense				3,800,000
Long-term debt, fair value				40,700,000					$ 40,700,000
Convertible debt | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse
Debt Instrument [Line Items]
Long-term debt, fair value				340,700,000					340,700,000
Debt instrument, unamortized premium			4,300,000
Long-term debt carrying value				279,000,000.0					279,000,000.0
Debt face amount				289,300,000					289,300,000
Gain (loss) on extinguishment of debt									10,300,000
Accrued and unpaid interest				1,400,000					1,400,000
Debt issuance costs, net				1,000,000.0					1,000,000.0
Payments of debt issuance costs									$ 1,200,000
Interest discount, basis spread on variable rate									0.0050
Repayments of convertible debt			70,000,000.0
Debt instrument, unamortized discount				$ 10,700,000					$ 10,700,000
Convertible debt | Additional Convertible Notes
Debt Instrument [Line Items]
Interest rate percentage				10.00%					10.00%
Debt face amount				$ 30,000,000.0					$ 30,000,000.0						$ 30,000,000.0
Convertible debt | Convertible Promissory Notes Interest Rate 10% Due December 2021
Debt Instrument [Line Items]
Repayments of convertible debt			70,000,000.0
Maximum borrowing capacity			150,000,000.0
Current borrowing capacity			$ 80,000,000.0
Term loan | Term Loan due December 2021, Non-Recourse
Debt Instrument [Line Items]
Unpaid Principal Balance								$ 117,947,000			$ 117,947,000						$ 121,784,000
Interest rate percentage								2.50%			2.50%						2.50%
Long-term debt carrying value								$ 117,145,000			$ 117,145,000						$ 120,437,000
Current portion of debt								7,609,000			7,609,000						5,122,000
Long-term portion of debt								$ 109,536,000			$ 109,536,000						$ 115,315,000
Term loan | Term Loan due November 2020, Recourse
Debt Instrument [Line Items]
Weighted average interest rate (as a percentage)								4.20%			4.20%						6.30%
Unpaid Principal Balance								$ 286,000			$ 286,000						$ 1,571,000
Interest rate percentage								4.00%			4.00%						4.00%
Long-term debt carrying value								$ 278,000			$ 278,000						$ 1,536,000
Current portion of debt								278,000			278,000						1,536,000
Long-term portion of debt								0			$ 0						0
Term loan | Term Loan due November 2020, Recourse | LIBOR
Debt Instrument [Line Items]
LIBOR margin (as a percentage)											4.00%
Senior secured notes | 2.5% green convertible senior notes due August 2025
Debt Instrument [Line Items]
Unpaid Principal Balance						$ 230,000,000.0		$ 230,000,000			$ 230,000,000
Interest rate percentage						2.50%		2.50%			2.50%
Long-term debt carrying value								$ 98,212,000			$ 98,212,000
Debt issuance costs, net						$ 9,900,000
Current portion of debt								0			0
Long-term portion of debt								98,212,000			$ 98,212,000
Debt instrument, unamortized discount						6,900,000
Debt other issuance costs, net						3,000,000.0
Proceeds from debt, net of issuance costs						220,100,000
Convertible, conversion ratio											0.0616808
Debt issuance costs, attributable to liability component, net						4,300,000
Debt issuance costs, attributable to equity component, net						5,600,000
Convertible, carrying amount of liability component						96,100,000
Convertible, carrying amount of equity component						133,900,000
Interest expense								$ 2,900,000			$ 2,900,000
Amortization of debt discount (premium)						2,100,000
Amortization of debt issuance costs						100,000
Interest rate percentage, attributable to liability component								0.212			0.212
Debt instrument, term											4 years 10 months 24 days
Contractual interest expense						$ 700,000
New Enterprise Associates 10, Limited Partnership | Convertible debt | Additional Convertible Notes
Debt Instrument [Line Items]
Total amount of loan proceeds									20,000,000.0
Foris Ventures LLC | Convertible debt | Additional Convertible Notes
Debt Instrument [Line Items]
Total amount of loan proceeds									10,000,000.0
Affiliated entity
Debt Instrument [Line Items]
Unpaid Principal Balance																	59,138,000
Long-term debt carrying value																	55,771,000
Current portion of debt																	24,683,000
Long-term portion of debt																	$ 31,088,000
Affiliated entity | Convertible promissory notes | Convertible Promissory Notes Interest Rate 5% Due December 2020, Recourse
Debt Instrument [Line Items]
Convertible stock price (in dollars per share) | $ / shares															$ 38.64
Affiliated entity | Convertible promissory notes | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse
Debt Instrument [Line Items]
Interest rate percentage																		6.00%
Embedded derivative, fair value, net				$ 24,000,000.0					$ 24,000,000.0
Affiliated entity | Convertible promissory notes | 10% convertible promissory notes due December 20211
Debt Instrument [Line Items]
Convertible stock price (in dollars per share) | $ / shares		$ 8.00						$ 8.00			$ 8.00
Affiliated entity | Convertible promissory notes | Convertible Promissory Notes Interest Rate 10% Due December 2021
Debt Instrument [Line Items]
Interest rate percentage				10.00%					10.00%
Covenant, proceeds used for certain transactions, percentage				50.00%					50.00%
Redemption price, percentage of principal amount redeemed									100.00%
Affiliated entity | Convertible debt | Convertible Promissory Notes Interest Rate 10% Due December 2021
Debt Instrument [Line Items]
Unpaid Principal Balance								$ 96,209,000			$ 96,209,000
Interest rate percentage				10.00%					10.00%
Debt instrument, unamortized premium								3,200,000			3,200,000			$ 3,200,000
Long-term debt carrying value								99,379,000			99,379,000
Debt instrument, deemed premium								$ 14,100,000			$ 14,100,000
Affiliated entity | Convertible debt | Convertible Promissory Notes Interest Rate 10% Due December 2021 | Subsequent Event
Debt Instrument [Line Items]
Unpaid Principal Balance													$ 96,200,000
Accrued and unpaid interest	$ 2,100,000
Debt conversion, shares issued (in shares) | shares					12,000,000.0
Redemption price, percentage of principal amount redeemed	104.00%
Class A common stock | Senior secured notes | 2.5% green convertible senior notes due August 2025
Debt Instrument [Line Items]
Convertible stock price (in dollars per share) | $ / shares						$ 16.21
On or before October 21, 2020 | Convertible promissory notes | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse
Debt Instrument [Line Items]
Redemption, applicable percentage				0					0
On or before October 21, 2020 | Maximum | Convertible promissory notes | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse
Debt Instrument [Line Items]
Redemption, applicable percentage				1					1
On or before October 21, 2020 | Minimum | Convertible promissory notes | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse
Debt Instrument [Line Items]
Redemption, applicable percentage				0					0
On or after October 21, 2020 | Maximum | Convertible promissory notes | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse
Debt Instrument [Line Items]
Redemption, applicable percentage				1					1
On or after October 21, 2020 | Minimum | Convertible promissory notes | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse
Debt Instrument [Line Items]
Redemption, applicable percentage				0.25					0.25
On or after March 27, 2022 | 10.25% senior secured notes due March 2027
Debt Instrument [Line Items]
Redemption price, percentage											108.00%
On or after March 27, 2023 | 10.25% senior secured notes due March 2027
Debt Instrument [Line Items]
Redemption price, percentage											104.00%
On or after March 27, 2024 | 10.25% senior secured notes due March 2027
Debt Instrument [Line Items]
Redemption price, percentage											102.00%
On or after March 27, 2026 | 10.25% senior secured notes due March 2027
Debt Instrument [Line Items]
Redemption price, percentage											100.00%