Related Party Transactions - Additional Information (Details) - USD ($)			1 Months Ended		12 Months Ended
	Aug. 31, 2017	Jul. 01, 2017	Jul. 31, 2018	Dec. 31, 2014	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013	Jun. 30, 2018	Jan. 18, 2018	Sep. 30, 2016	Sep. 20, 2016	Sep. 10, 2016	Jun. 30, 2016	Jan. 29, 2016	Dec. 15, 2015	Dec. 31, 2012
Related Party Transaction [Line Items]
Long-term debt carrying value					$ 741,281,000	$ 941,341,000
Unpaid principal balance					786,495,000	1,008,104,000
Interest paid					$ 39,465,000	21,948,000	$ 20,549,000
Issuance of common stock upon exercise of warrants (in shares)					312,575
Affiliated entity
Related Party Transaction [Line Items]
Long-term debt carrying value					$ 64,100,000	107,000,000
Issuance of common stock warrant	$ 9,400,000
Softbank Corp.
Related Party Transaction [Line Items]
Accounts receivable					3,300,000	0
Consulting Agreement | General Colin L. Powell | Director
Related Party Transaction [Line Items]
Related party amount of transaction					$ 125,000
Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse
Related Party Transaction [Line Items]
Interest rate percentage										5.00%
Unpaid principal balance			$ 221,600,000
Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse | Affiliated entity
Related Party Transaction [Line Items]
Debt term				3 years
Debt face amount				$ 132,200,000										$ 193,200,000.0
Interest rate percentage				8.00%
Convertible stock price (in dollars per share)			$ 38.64		$ 38.64
Unpaid principal balance						38,300,000			$ 40,100,000
Convertible promissory notes | Convertible Promissory Notes due December 2019 and 2020, Recourse | Alberta Investment Management Corporation | Affiliated entity
Related Party Transaction [Line Items]
Debt face amount				$ 10,000,000
Convertible promissory notes | Convertible Promissory Notes due December 2020, Recourse
Related Party Transaction [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)					$ 20.61											$ 11.25
Convertible promissory notes | Convertible Promissory Notes due December 2020, Recourse | Affiliated entity
Related Party Transaction [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
Debt interest increase (as a percentage)		1.00%
Term loan | Term Loan due September 2028, Non-Recourse
Related Party Transaction [Line Items]
Long-term debt carrying value					$ 36,319,000	36,940,000
Interest rate percentage					7.50%
Unpaid principal balance					$ 40,538,000	41,927,000
PPA Company IIIa
Related Party Transaction [Line Items]
Repayments of debt					$ 4,431,000	3,041,000	$ 2,129,000
PPA Company IIIa | Term loan | Term Loan due September 2028, Non-Recourse
Related Party Transaction [Line Items]
Debt face amount																	$ 46,800,000
Interest rate percentage					7.50%												7.50%
PPA Company IIIa | Term loan | Term Loan due September 2028, Non-Recourse | Affiliated entity
Related Party Transaction [Line Items]
Debt face amount				$ 45,000,000
Unpaid principal balance					$ 40,500,000	41,900,000
Repayments of debt					1,400,000	900,000
Interest paid					$ 3,100,000	3,200,000	$ 3,300,000
Common stock warrants
Related Party Transaction [Line Items]
Number of securities called by warrants (in shares)				33,333
Revaluation of warrants								$ 3,300,000
Common stock warrants | Affiliated entity
Related Party Transaction [Line Items]
Revaluation of warrants						$ 200,000
Common stock warrants | CPPIB | Affiliated entity
Related Party Transaction [Line Items]
Number of securities called by warrants (in shares)	312,888
Maximum | Common stock warrants | J.P. Morgan
Related Party Transaction [Line Items]
Number of securities called by warrants (in shares)							146,666
Maximum | Common stock warrants | J.P. Morgan | Affiliated entity
Related Party Transaction [Line Items]
Number of securities called by warrants (in shares)							146,666
Maximum | Common stock warrants | CPPIB
Related Party Transaction [Line Items]
Number of securities called by warrants (in shares)							166,222
Maximum | Common stock warrants | CPPIB | Affiliated entity
Related Party Transaction [Line Items]
Number of securities called by warrants (in shares)							166,222
Series G preferred
Related Party Transaction [Line Items]
Debt conversion, shares issued (in shares)			1,038,050