Commitments and Contingencies - Additional Information (Details)	3 Months Ended	12 Months Ended			106 Months Ended
	Dec. 31, 2020 USD ($) ft² numberOfEmployees	Dec. 31, 2020 USD ($) ft² numberOfEmployees	Dec. 31, 2019 USD ($) numberOfEmployees	Dec. 31, 2018 USD ($)	Dec. 31, 2020 USD ($) ft² numberOfEmployees	Mar. 31, 2020 USD ($)	Sep. 30, 2017 USD ($) numberOfEmployees	Jun. 30, 2015 USD ($)	Mar. 31, 2012 USD ($)
Operating Leased Assets [Line Items]
Term of customer contract for negotiated rates		15 years
Area of real estate property | ft²	370,601	370,601			370,601
Operating leases, rent expense			$ 7,800,000	$ 6,300,000
Restricted Cash	$ 169,763,000	$ 169,763,000	174,565,000		$ 169,763,000
Grants receivable									$ 16,500,000
Number of employees to be hired per incentive grant agreement | numberOfEmployees							900
Minimum cumulative employee compensation, recapture period one							$ 108,000,000.0
Minimum cumulative employee compensation, recapture period three							$ 324,000,000.0
Cumulative compensation expense incurred	152,200,000	152,200,000	120,100,000		152,200,000
Proceeds from government grants					12,000,000.0
Grant agreement, maximum possible repayment amount, recapture period two	2,000,000.0	2,000,000.0			2,000,000.0
Grant agreement, maximum possible repayment amount, recapture period three	2,500,000	2,500,000			2,500,000
Grant agreement, recapture provision repayments	1,500,000	1,500,000			1,500,000
Delaware grant obligation	9,212,000	9,212,000	$ 10,469,000		9,212,000
Payment for civil penalty		200,000
Civil penalty accrual						$ 1,200,000
Civil penalty expense	1,200,000
PPA II | PPA Entities
Operating Leased Assets [Line Items]
Restricted Cash	$ 108,700,000	$ 108,700,000			$ 108,700,000
PPA IIIb | PPA Entities
Operating Leased Assets [Line Items]
Pledged assets, term			7 years
Cash and cash equivalents, period increase (decrease)			$ 20,000,000.0
Delaware
Operating Leased Assets [Line Items]
Number of full time employees | numberOfEmployees	424	424	323		424
PPA V
Operating Leased Assets [Line Items]
PPA expenses		$ 7,400,000	$ 3,500,000
Term loan | PPA V | Term Loan due December 2021, Non-Recourse
Operating Leased Assets [Line Items]
Debt face amount								$ 131,200,000
Letters of Credit | PPA V
Operating Leased Assets [Line Items]
Maximum borrowing capacity	$ 6,200,000	6,200,000			$ 6,200,000			$ 6,400,000
Amount outstanding	$ 5,200,000	$ 5,200,000	$ 5,000,000.0		$ 5,200,000