Summary of Significant Accounting Policies - Deferred Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
Power purchase or lease agreement term	20 years
Deferred revenue	$ 591,625	$ 564,852	$ 525,400
Deferred revenue, revenue recognized	52,900	47,700	$ 42,400
Contracted but not yet recognized	$ 5,288,700
Revenue expected to recognize over next twelve months, percent	6.00%
Revenue recognized, term, existing deferred revenue	10 years
Residential solar energy systems
Deferred Revenue Arrangement [Line Items]
Residential solar energy system, average age	3 years
Minimum
Deferred Revenue Arrangement [Line Items]
Power purchase or lease agreement term	20 years
Revenue recognized, term	20 years
Maximum
Deferred Revenue Arrangement [Line Items]
Power purchase or lease agreement term	25 years
Revenue recognized, term	25 years
Under Customer Agreements
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 576,727	548,280
Under Customer Agreements | Payments received
Deferred Revenue Arrangement [Line Items]
Deferred revenue	538,926	517,544
Under Customer Agreements | Financing component balance
Deferred Revenue Arrangement [Line Items]
Deferred revenue	37,801	30,736
Under SREC contracts
Deferred Revenue Arrangement [Line Items]
Deferred revenue	14,898	16,572
Under SREC contracts | Payments received
Deferred Revenue Arrangement [Line Items]
Deferred revenue	12,977	14,805
Under SREC contracts | Financing component balance
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 1,921	$ 1,767