Outstanding Loans and Security Agreements - Recourse Debt Facilities (Additional Information) (Details)	1 Months Ended	6 Months Ended	19 Months Ended
	Jul. 31, 2018 USD ($) shares	Jun. 30, 2019 USD ($) day $ / shares shares	Jun. 30, 2016 USD ($)	Dec. 31, 2018 USD ($)	Jan. 18, 2018	Aug. 31, 2017 shares	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 10, 2016 USD ($) $ / shares	Jan. 29, 2016 USD ($)	Dec. 15, 2015 USD ($) $ / shares	Dec. 31, 2014	May 31, 2013 USD ($)
Debt Instrument [Line Items]
Long-term debt carrying value		$ 668,207,000		$ 741,281,000
Unpaid principal balance		701,278,000		786,495,000
Long-term portion of debt		641,983,000		711,433,000
Indebtedness in excess of		$ 300,000
Issuance of common stock upon exercise of warrants (in shares) | shares		312,575
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		$ 121,952,000		123,384,000
Interest rate percentage		2.50%
Unpaid principal balance		$ 123,664,000		125,456,000
Long-term portion of debt		$ 118,058,000		$ 119,712,000
Term loan | Term Loan due November 2020, Recourse
Debt Instrument [Line Items]
Debt face amount														$ 12,000,000.0
Weighted average interest rate (as a percentage)		6.50%		5.90%
Long-term debt carrying value		$ 2,376,000		$ 3,214,000
Interest rate percentage		4.00%
Unpaid principal balance		$ 2,429,000		3,286,000
Long-term portion of debt		695,000		1,528,000
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		$ 35,576,000		34,706,000
Interest rate percentage		5.00%
Unpaid principal balance		$ 33,104,000		33,104,000
Long-term portion of debt		$ 35,576,000		34,706,000
Convertible promissory notes | Convertible Promissory Notes Interest Rate 8% Due December 2018
Debt Instrument [Line Items]
Debt term			3 years
Convertible promissory notes | Convertible Promissory Notes due December 2020, Recourse
Debt Instrument [Line Items]
Debt face amount										$ 75,000,000	$ 25,000,000	$ 160,000,000
Interest rate percentage		6.00%
Convertible stock price (in dollars per share) | $ / shares		$ 11.25								$ 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		$ 271,503,000		263,284,000
Interest rate percentage		6.00%
Convertible stock price (in dollars per share) | $ / shares		$ 11.25
Unpaid principal balance		$ 296,233,000		296,233,000
Long-term portion of debt		271,503,000		263,284,000
Notes | Notes due July 2024, Recourse
Debt Instrument [Line Items]
Debt face amount							$ 100,000,000.0
Long-term debt carrying value		$ 96,384,000		95,555,000
Interest rate percentage		10.00%					10.00%
Unpaid principal balance		$ 100,000,000		100,000,000
Long-term portion of debt		82,384,000		88,555,000
Affiliated entity
Debt Instrument [Line Items]
Long-term debt carrying value		63,266,000		64,053,000
Unpaid principal balance		67,051,000		68,272,000
Long-term portion of debt		$ 60,377,000		61,853,000
Affiliated entity | Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse
Debt Instrument [Line Items]
Debt face amount			$ 193,200,000.0
Interest rate percentage					8.00%								8.00%
Convertible stock price (in dollars per share) | $ / shares		$ 38.64
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%		5.00%
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 promissory notes | Convertible Promissory Notes Interest Rate 6% Due December 2020, Recourse
Debt Instrument [Line Items]
Long-term debt carrying value		27,734,000		27,734,000
Unpaid principal balance		27,734,000		27,734,000
Long-term portion of debt		$ 27,734,000		$ 27,734,000
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
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