Summary of Significant Accounting Policies - (Additional Information) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2021	Aug. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit		$ (3,177,381)		$ (3,177,381)		$ (3,103,937)
Additional paid in capital		(3,155,917)		(3,155,917)		(3,182,753)
Non-recourse long term debt, non-current	[1]	98,093		$ 98,093		102,045
Revenue related to sales-type leases						2,300	$ 2,900	$ 3,400
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of PPA				10 years
Term during which the Company is responsible for the installation, operation and maintenance of the Energy Servers				10 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of PPA				21 years
Term during which the Company is responsible for the installation, operation and maintenance of the Energy Servers				15 years
Electricity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, lease income		$ 16,310	$ 15,540	$ 32,716	$ 30,843
Power Purchase Agreement Program Leases | Electricity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, lease income						27,700	29,700	30,900
Power Purchase Agreement Program Leases | Service
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, lease income						$ 13,800	$ 14,600	$ 15,200
2.5% Green Convertible Senior Notes due August 2025 | Senior secured notes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest rate percentage		2.50%		2.50%		2.50%				2.50%
2.5% Green Convertible Senior Notes due August 2025 | Senior secured notes | Accounting Standards Update 2020-06
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit									$ 5,300
Additional paid in capital									126,800
Non-recourse long term debt, non-current									$ 121,500

[1] We have variable interest entities, which represent a portion of the consolidated balances recorded within these financial statement line items in the condensed consolidated balance sheets (see Note 11 - Portfolio Financings).