Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2018 USD ($) business_activity segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2018 USD ($)	Jan. 01, 2017 USD ($)	Jan. 01, 2016 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | segment		1
Number of business activities | business_activity		1
Bad debt expense		$ 3,400	$ 2,100	$ 1,400
Uncollectible receivables written off		$ 2,800	1,600	1,800
Power purchase or lease agreement term		20 years
Customer Agreements, initial set up, discount percent		10.00%
Capitalized additional costs associated with software		$ 2,500	6,100	$ 4,900
Deferred tax assets, gross		352,038	238,601
Cumulative effect of adoption					$ 1,992	$ 2,996	$ 86,461
Solar materials purchases from top five suppliers		$ 221,500	$ 188,800
Minimum
Summary Of Significant Accounting Policies [Line Items]
Power purchase or lease agreement term		20 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Power purchase or lease agreement term		25 years
Inverters
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life		10 years
Solar energy systems
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life	20 years	35 years
Solar energy systems | Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life		35 years
Retained Earnings (Accumulated Deficit)
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of adoption						2,996	$ 86,368
Retained Earnings (Accumulated Deficit) | Accounting Standards Update 2016-16
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of adoption						300
Retained Earnings (Accumulated Deficit) | Accounting Standards Update 2016-09
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of adoption						3,300
Adjustment | Accounting Standards Update 2016-16
Summary Of Significant Accounting Policies [Line Items]
Prepaid taxes						(378,500)
Deferred tax assets, gross						$ 378,200