|
Derivative Instruments - Additional information (Detail) (USD $)
In Millions, unless otherwise specified |
12 Months Ended |
|---|---|
|
Dec. 31, 2013
|
|
| Derivative [Line Items] | |
| Fair value of commodity derivatives net liability | $ 10.6 |
| Derivative contracts terminated | 10.7 |
| Expected premium payments in 2014 | 5.0 |
| Maximum amount of loss in the event of all counterparties defaulting | $ 0.6 |