Stock-Based Compensation - Additional Information (Details)		1 Months Ended		3 Months Ended
	Nov. 07, 2018 USD ($) solar_energy_system_install	Aug. 31, 2017 USD ($) solar_energy_system_install $ / shares shares	Jul. 31, 2015 USD ($) shares	Mar. 31, 2019 purchase_period
Warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant, term		40 months
Warrant, number purchased | shares		11,793,355
Warrant, exercise price (in dollars per share) | $ / shares		$ 0.01
Warrant, vesting percentage		50.05%
Warrant, milestone one, solar energy systems | solar_energy_system_install	6,000	30,000
Warrant, milestone two, marketing and sales dollars | $		$ 10,000,000.0
Warrant, vesting term		5 years
Warrant, milestone two, solar energy systems | solar_energy_system_install	8,000	6,000
Warrant, vesting percentage, milestone one	10.00%
Warrant, vesting percentage, milestone two	13.30%
Warrant, milestone one and two, marketing and sales dollars | $	$ 25,000,000.0
Warrant, vesting percentage, milestone three	8.30%
Warrant, milestone three, solar energy systems | solar_energy_system_install	5,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP offering period				24 months
Number of purchase periods | purchase_period				4
Maximum percentage in payroll deductions to acquire shares of common stock			15.00%
Maximum deductible fair market value of shares available for employee to purchase per calendar year | $			$ 25,000
Maximum number of shares available for employee to purchase per offering period | shares			10,000