Income Taxes - Additional Information (Details) $ in Millions	3 Months Ended	36 Months Ended
	Mar. 31, 2019 USD ($) solar_generator_unit investor	Dec. 31, 2015 USD ($) fund tax_opinion	Mar. 31, 2018 USD ($)
Income Tax Disclosure [Abstract]
Uncertain tax position, accrued interest	$ 1.9		$ 1.8
Number of federal renewable energy tax credit funds | fund		3
Federal tax credit benefit		$ 22.8
Number of tax opinions | tax_opinion		2
Number of DC solar fund investors | investor	10
Percentage of solar generator units positively identified (over)	91.00%
Number of solar generator units | solar_generator_unit	512
Increase to the provision for income taxes	$ 12.1
Estimated loss on the related tax positions	$ 28.8