Commitments and Contingencies - Additional Information (Detail)
$ in Millions |
|
|
9 Months Ended |
|
Sep. 21, 2016
USD ($)
MW
|
Jun. 30, 2016
USD ($)
kV
MW
|
Sep. 30, 2016
USD ($)
|
| Power Sale Agreements [Member] |
|
|
|
| Other Commitments [Line Items] |
|
|
|
| Letters of credit issued |
|
|
$ 107.0
|
| Power Sale Agreements [Member] | Minimum [Member] |
|
|
|
| Other Commitments [Line Items] |
|
|
|
| Termination Date |
|
|
2019
|
| Power Sale Agreements [Member] | Maximum [Member] |
|
|
|
| Other Commitments [Line Items] |
|
|
|
| Termination Date |
|
|
2039
|
| Project Finance Agreements [Member] |
|
|
|
| Other Commitments [Line Items] |
|
|
|
| Letters of credit issued |
|
|
$ 108.8
|
| Turbine Availability Warranty and Service Guarantee [Member] |
|
|
|
| Other Commitments [Line Items] |
|
|
|
| Loss contingency accrual |
|
|
$ 3.4
|
| Broadview [Member] |
|
|
|
| Other Commitments [Line Items] |
|
|
|
| Ownership interest committed to acquire |
|
84.00%
|
|
| Generating capacity | MW |
|
324
|
|
| Purchase Obligation |
|
$ 269.0
|
|
| Western Interconnect transmission line [Member] |
|
|
|
| Other Commitments [Line Items] |
|
|
|
| Ownership interest committed to acquire |
|
99.00%
|
|
| Transmission-level voltage | kV |
|
345
|
|
| Armow [Member] |
|
|
|
| Other Commitments [Line Items] |
|
|
|
| Ownership interest committed to acquire |
50.00%
|
|
|
| Generating capacity | MW |
179
|
|
|
| Purchase Obligation |
$ 133.0
|
|
|