|
Derivative Instruments - Location and Amounts of Derivative Gains and Losses in Condensed Consolidated Statements of Income (Details) (USD $)
In Thousands, unless otherwise specified |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2014
|
Dec. 31, 2013
|
Dec. 31, 2012
|
|
| Derivative Instruments, Gain (Loss) [Line Items] | |||
| Amount of Gain or (Loss) Recognized in Income on Derivative | $ 46,212 | $ (9,851) | $ (12,365) |
| Derivatives not designated as hedging instruments | Commodity Contract | Net realized and unrealized gains (losses) on fuel price derivatives | |||
| Derivative Instruments, Gain (Loss) [Line Items] | |||
| Amount of Gain or (Loss) Recognized in Income on Derivative | $ 46,212 | $ (9,851) | |