Significant Accounting Policies - Performance Obligations (Details) $ in Billions	9 Months Ended
	Sep. 30, 2020 USD ($)
Accounting Policies [Abstract]
Contracted but not yet recognized revenue	$ 1.4
Performance obligation, description of timing	We do not expect the annual recognition to vary significantly over approximately the next 20 years as the vast majority of existing solar service agreements have at least 20 years remaining
Average age of solar systems	3 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contracted but not yet recognized revenue, percentage	4.00%
Contracted but not yet recognized revenue, expected timing of satisfaction	12 months