Outstanding Loans and Security Agreements - Recourse Debt Facilities (Additional Information) (Details)			1 Months Ended	9 Months Ended
	Jul. 01, 2017	May 22, 2013 USD ($)	Dec. 31, 2014 USD ($) related_party shares	Sep. 30, 2018 USD ($) $ / shares shares	Jul. 27, 2018 USD ($) $ / shares	Jun. 30, 2018 USD ($)	Jan. 18, 2018	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($) agreement	Aug. 31, 2017 shares	Dec. 31, 2016 shares	Sep. 30, 2016 USD ($) agreement	Sep. 20, 2016 USD ($)	Sep. 10, 2016 USD ($)	Jan. 29, 2016 USD ($)	Dec. 15, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($)	Feb. 28, 2015 USD ($) agreement
Debt Instrument [Line Items]
Long-term debt carrying value				$ 740,811,000				$ 941,341,000
Unpaid principal balance				$ 792,713,000				1,008,104,000
Issuance of common stock upon exercise of warrants (in shares) | shares				312,575
Long-term portion of debt				$ 718,889,000				$ 921,205,000
Notes due July 2024, Recourse
Debt Instrument [Line Items]
Interest rate percentage				10.00%				10.00%
Term loan | Term Loan due November 2020, Recourse
Debt Instrument [Line Items]
Debt face amount		$ 12,000,000
Debt term		90 months
Weighted average interest rate (as a percentage)								5.10%
Long-term debt carrying value				$ 3,631,000				$ 4,887,000
Unpaid principal balance				3,631,000				5,000,000
Long-term portion of debt				1,945,000				3,197,000
Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse
Debt Instrument [Line Items]
Debt term			3 years
Long-term debt carrying value				$ 34,273,000
Interest rate percentage				5.00%			5.00%
Number of related parties | related_party			3
Unpaid principal balance				$ 34,273,000	$ 221,600,000
Long-term portion of debt				34,273,000				244,700,000
Convertible promissory notes | Convertible Promissory Notes, January and February 2015, Recoursee
Debt Instrument [Line Items]
Debt face amount																		$ 34,000,000
Number of agreements | agreement																		2
Convertible promissory notes | Convertible Promissory Notes, June 2015, Recourse
Debt Instrument [Line Items]
Debt face amount																	$ 27,000,000
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
Long-term debt carrying value				$ 258,862,000				$ 236,724,000
Interest rate percentage	6.00%			6.00%				6.00%
Convertible stock price (in dollars per share) | $ / shares				$ 46.37												$ 11.25
Unpaid principal balance				$ 296,233,000				$ 286,069,000
Long-term portion of debt				258,862,000				236,724,000
Notes | Notes due July 2024, Recourse
Debt Instrument [Line Items]
Debt face amount									$ 100,000,000
Long-term debt carrying value				95,451,000				94,517,000
Interest rate percentage									10.00%
Unpaid principal balance				100,000,000				100,000,000
Long-term portion of debt				95,451,000				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				$ 68,700,000				107,000,000
Affiliated entity | Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse
Debt Instrument [Line Items]
Debt face amount			$ 132,200,000
Debt term			3 years
Interest rate percentage			8.00%
Convertible stock price (in dollars per share) | $ / shares				$ 38.64	$ 38.64
Unpaid principal balance						$ 39,900,000		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
Number of agreements | agreement												5
Debt interest increase (as a percentage)	1.00%
Affiliated entity | Alberta Investment Management Corporation | Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse
Debt Instrument [Line Items]
Debt face amount			$ 10,000,000
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
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