Derivative Instruments - Additional Information (Detail)
$ in Thousands |
3 Months Ended |
|
|
|
Mar. 31, 2018
USD ($)
MW
|
Mar. 31, 2017
USD ($)
|
Dec. 31, 2017
USD ($)
MW
|
Dec. 31, 2010
MW
|
| Derivative [Line Items] |
|
|
|
|
| AOCL to be reclassified within 12 months |
$ 4,600
|
|
|
|
| Funds deposited by counterparty |
17,744
|
|
$ 29,780
|
|
| Counterparty deposit liability |
17,744
|
|
$ 29,780
|
|
| Other reclassifications to net loss |
$ 1,396
|
$ 2,319
|
|
|
| Undesignated Derivative Instruments [Member] | Energy derivative [Member] |
|
|
|
|
| Derivative [Line Items] |
|
|
|
|
| Nonmonetary notional amount | MW |
556,858
|
|
697,471
|
504,220
|
| Minimum [Member] | Designated as Hedging Instrument [Member] | Interest rate swaps [Member] |
|
|
|
|
| Derivative [Line Items] |
|
|
|
|
| Derivative, Remaining Maturity |
69 months
|
|
|
|
| Minimum [Member] | Undesignated Derivative Instruments [Member] | Foreign currency forward contracts [Member] |
|
|
|
|
| Derivative [Line Items] |
|
|
|
|
| Derivative, Remaining Maturity |
3 months
|
|
|
|
| Maximum [Member] | Designated as Hedging Instrument [Member] | Interest rate swaps [Member] |
|
|
|
|
| Derivative [Line Items] |
|
|
|
|
| Derivative, Remaining Maturity |
249 months
|
|
|
|
| Maximum [Member] | Undesignated Derivative Instruments [Member] | Interest rate swaps [Member] |
|
|
|
|
| Derivative [Line Items] |
|
|
|
|
| Derivative, Remaining Maturity |
147 months
|
|
|
|
| Maximum [Member] | Undesignated Derivative Instruments [Member] | Foreign currency forward contracts [Member] |
|
|
|
|
| Derivative [Line Items] |
|
|
|
|
| Derivative, Remaining Maturity |
144 months
|
|
|
|