|
Derivatives (Disclosure Of Fair Value Of Derivatives) (Details) (USD $)
In Thousands, unless otherwise specified
|
Mar. 31, 2015
|
Dec. 31, 2014
|
| Derivative [Line Items] |
|
|
| Derivative Asset, Fair Value, Gross Liability |
$ (136,148) |
$ (98,686) |
| Derivative Liability, Fair Value, Gross Asset |
136,148 |
98,686 |
| Derivative Asset |
18,856 |
13,557 |
| Derivative Liability |
(1,010) |
(766) |
| Net derivatives as classified in the balance sheet |
17,846 |
12,791 |
| Not Designated as Hedging Instrument [Member] |
|
|
| Derivative [Line Items] |
|
|
| Price Risk Derivative Instruments Not Designated as Hedging Instruments Asset, at Fair Value |
148,108 |
105,708 |
| Price Risk Derivative Instruments Not Designated as Hedging Instruments Liability, at Fair Value |
(137,051) |
(96,960) |
| Not Designated as Hedging Instrument [Member] | Coal Contract [Member] |
|
|
| Derivative [Line Items] |
|
|
| Derivative Assets |
126,397 |
96,898 |
| Derivative Liabilities |
(125,204) |
(93,272) |
| Heating Oil-Diesel Purchases [Member] | Not Designated as Hedging Instrument [Member] |
|
|
| Derivative [Line Items] |
|
|
| Price Risk Derivative Instruments Not Designated as Hedging Instruments Asset, at Fair Value |
4,079 |
300 |
| Coal Contract [Member] | Designated as Hedging Instrument [Member] |
|
|
| Derivative [Line Items] |
|
|
| Derivative Assets |
6,896 |
6,535 |
| Derivative Liabilities |
(107) |
(2,492) |
| Coal Contract [Member] | Not Designated as Hedging Instrument [Member] |
|
|
| Derivative [Line Items] |
|
|
| Price Risk Derivative Instruments Not Designated as Hedging Instruments Asset, at Fair Value |
16,484 |
8,510 |
| Price Risk Derivative Instruments Not Designated as Hedging Instruments Liability, at Fair Value |
(11,094) |
(3,688) |
| Natural Gas [Member] | Not Designated as Hedging Instrument [Member] |
|
|
| Derivative [Line Items] |
|
|
| Price Risk Derivative Instruments Not Designated as Hedging Instruments Asset, at Fair Value |
1,148 |
0 |
| Price Risk Derivative Instruments Not Designated as Hedging Instruments Liability, at Fair Value |
(753) |
0 |
| Price Risk Derivative [Member] |
|
|
| Derivative [Line Items] |
|
|
| Derivative Assets |
155,004 |
112,243 |
| Derivative Liabilities |
$ (137,158) |
$ (99,452) |