Commitments and Contingencies - Additional Information (Details) $ in Millions		3 Months Ended	12 Months Ended
	Aug. 08, 2018 USD ($)	Mar. 31, 2019 USD ($) contract	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)
Other Commitments [Line Items]
Letters of credit outstanding, amount		$ 14.4	$ 9.7
Purchase commitment		$ 60.6
Corporate office space | San Francisco, California and Denver, Colorado
Other Commitments [Line Items]
Operating lease agreements | contract		2
Minimum | Corporate office space | San Francisco, California and Denver, Colorado
Other Commitments [Line Items]
Lease agreement terms		5 years
Maximum | Corporate office space | San Francisco, California and Denver, Colorado
Other Commitments [Line Items]
Lease agreement terms		7 years
Letter of Credit | Minimum
Other Commitments [Line Items]
Letter of credit, fee percentage		2.75%	2.50%
Letter of Credit | Maximum
Other Commitments [Line Items]
Letter of credit, fee percentage		3.25%	3.25%
Settled litigation | Slovin et al. v. Sunrun Inc. and Clean Energy Experts, LLC
Other Commitments [Line Items]
Settlement amount, accrual				$ 5.5
Settled litigation | Fink, et al. v. Sunrun Inc., et al.
Other Commitments [Line Items]
Settlement amount	$ 2.5