Outstanding Loans and Security Agreements - Recourse Debt Facilities (Additional Information) (Details)		1 Months Ended		12 Months Ended	19 Months Ended
	May 22, 2013 USD ($)	Jul. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2018 USD ($) day agreement $ / shares shares	Jun. 30, 2016 USD ($)	Jun. 30, 2018 USD ($)	Jan. 18, 2018	Dec. 31, 2017 USD ($)	Aug. 31, 2017 shares	Jul. 01, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($) shares	Sep. 30, 2016 USD ($)	Sep. 20, 2016 USD ($)	Sep. 10, 2016 USD ($)	Jan. 29, 2016 USD ($)	Dec. 15, 2015 USD ($) $ / shares	May 31, 2013 USD ($)
Debt Instrument [Line Items]
Long-term debt carrying value				$ 741,281,000				$ 941,341,000
Unpaid principal balance				786,495,000				1,008,104,000
Long-term portion of debt				711,433,000				921,205,000
Indebtedness in excess of				$ 300,000
Issuance of common stock upon exercise of warrants (in shares) | shares				312,575
Notes due July 2024, Recourse
Debt Instrument [Line Items]
Interest rate percentage				10.00%
Credit facility | Term Loan due November 2020, Recourse
Debt Instrument [Line Items]
Debt face amount												$ 5,000,000.0						$ 5,000,000.0
Term loan | Term Loan due December 2021, Non-Recourse
Debt Instrument [Line Items]
Long-term debt carrying value				$ 123,384,000				125,596,000
Interest rate percentage				2.50%
Unpaid principal balance				$ 125,456,000				128,403,000
Long-term portion of debt				$ 119,712,000				$ 122,650,000
Term loan | Term Loan due November 2020, Recourse
Debt Instrument [Line Items]
Debt face amount	$ 12,000,000																	$ 12,000,000.0
Debt term	90 months
Weighted average interest rate (as a percentage)				5.90%				5.10%
Long-term debt carrying value				$ 3,214,000				$ 4,887,000
Interest rate percentage				4.00%
Unpaid principal balance				$ 3,286,000				5,000,000
Long-term portion of debt				1,528,000				3,197,000
Indebtedness in excess of				100,000
Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse
Debt Instrument [Line Items]
Interest rate percentage							5.00%
Unpaid principal balance		$ 221,600,000
Convertible promissory notes | Convertible Promissory Notes Interest Rate 5% Due December 2020, Recourse
Debt Instrument [Line Items]
Long-term debt carrying value				$ 34,706,000
Interest rate percentage				5.00%
Unpaid principal balance				$ 33,104,000
Long-term portion of debt				$ 34,706,000
Convertible promissory notes | Convertible Promissory Notes Interest Rate 8% Due December 2018
Debt Instrument [Line Items]
Debt term					3 years
Long-term debt carrying value								244,717,000
Interest rate percentage				8.00%
Unpaid principal balance								244,717,000
Long-term portion of debt								244,717,000
Convertible promissory notes | Convertible Promissory Notes due December 2020, Recourse
Debt Instrument [Line Items]
Debt face amount														$ 75,000,000	$ 75,000,000	$ 25,000,000	$ 160,000,000
Interest rate percentage				6.00%						6.00%
Convertible stock price (in dollars per share) | $ / shares				$ 20.61													$ 11.25
Convertible promissory notes | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse
Debt Instrument [Line Items]
Long-term debt carrying value				$ 263,284,000				236,724,000
Interest rate percentage				6.00%
Convertible stock price (in dollars per share) | $ / shares				$ 11.25
Unpaid principal balance				$ 296,233,000				286,069,000
Long-term portion of debt				263,284,000				236,724,000
Notes | Notes due July 2024, Recourse
Debt Instrument [Line Items]
Debt face amount											$ 100,000,000
Long-term debt carrying value				$ 95,555,000				94,517,000
Interest rate percentage				10.00%
Unpaid principal balance				$ 100,000,000				100,000,000
Long-term portion of debt				$ 88,555,000				94,517,000
Number of agreements | agreement				5
Convertible redeemable common stock warrants
Debt Instrument [Line Items]
Number of securities called by warrants (in shares) | shares			33,333
Affiliated entity
Debt Instrument [Line Items]
Long-term debt carrying value				$ 64,100,000				107,000,000
Affiliated entity | Term Loan due December 2021, Non-Recourse
Debt Instrument [Line Items]
Interest rate percentage				2.50%
Affiliated entity | Term Loan due November 2020, Recourse
Debt Instrument [Line Items]
Interest rate percentage				4.00%
Affiliated entity | Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse
Debt Instrument [Line Items]
Debt face amount			$ 132,200,000		$ 193,200,000.0
Debt term			3 years
Interest rate percentage			8.00%
Convertible stock price (in dollars per share) | $ / shares		$ 38.64		$ 38.64
Unpaid principal balance						$ 40,100,000		38,300,000
Affiliated entity | Convertible promissory notes | Convertible Promissory Notes due December 2020, Recourse
Debt Instrument [Line Items]
Debt face amount													$ 260,000,000
Interest rate percentage										6.00%		6.00%	5.00%
Unpaid principal balance				$ 27,700,000				$ 26,800,000
Percentage of debt outstanding to maintain as collateral										200.00%
Holders of debt, percentage subject to cross-acceleration provision										25.00%
Indebtedness in excess of										$ 15,000,000.0
Affiliated entity | Convertible redeemable common stock warrants | CPPIB
Debt Instrument [Line Items]
Number of securities called by warrants (in shares) | shares									312,888
Maximum | Convertible redeemable common stock warrants | J.P. Morgan
Debt Instrument [Line Items]
Number of securities called by warrants (in shares) | shares												146,666
Maximum | Convertible redeemable common stock warrants | CPPIB
Debt Instrument [Line Items]
Number of securities called by warrants (in shares) | shares												166,222
Maximum | Affiliated entity | Convertible redeemable common stock warrants | J.P. Morgan
Debt Instrument [Line Items]
Number of securities called by warrants (in shares) | shares												146,666
Maximum | Affiliated entity | Convertible redeemable common stock warrants | CPPIB
Debt Instrument [Line Items]
Number of securities called by warrants (in shares) | shares												166,222
Class B common stock
Debt Instrument [Line Items]
Debt conversion, shares issued (in shares) | shares		5,734,440
On or after July 27, 2020 | Affiliated entity | Convertible promissory notes | Convertible Promissory Notes due December 2020, Recourse
Debt Instrument [Line Items]
Last reported sale price of common stock (at least) (in dollars per share) | $ / shares				$ 22.50
Trading days (at least) | day				20
Period of consecutive trading days | day				30
Trading days immediately preceding redemption date | day				3