Solar Energy Systems, Leased and To Be Leased - Net - Components of Solar Energy Systems, Leased and to Be Leased (Parenthetical) (Detail) - USD ($) $ in Millions |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Capital Leased Assets [Line Items] | ||
| Accumulated depreciation on capital leased assets | $ 40.2 | $ 22.7 |
| Solar Energy Systems [Member] | ||
| Capital Leased Assets [Line Items] | ||
| Capital leased assets | 36.0 | |
| Accumulated depreciation on capital leased assets | 0.2 | |
| Energy Storage Systems [Member] | ||
| Capital Leased Assets [Line Items] | ||
| Capital leased assets | 21.3 | |
| Accumulated depreciation on capital leased assets | $ 0.1 |