Summary of Significant Accounting Policies - Estimated Useful Lives of Respective Assets (Detail) |
12 Months Ended |
|---|---|
Dec. 31, 2020 | |
| Minimum [Member] | Solar energy systems leased and to be leased [Member] | |
| Property Plant And Equipment [Line Items] | |
| Solar energy systems in service | 30 years |
| Maximum [Member] | |
| Property Plant And Equipment [Line Items] | |
| Initial direct costs related to customer solar energy system lease acquisition costs | 25 years |
| Maximum [Member] | Solar energy systems leased and to be leased [Member] | |
| Property Plant And Equipment [Line Items] | |
| Solar energy systems in service | 35 years |