|
Asset Retirement Obligation (Details) (USD $)
|
12 Months Ended | |
|---|---|---|
|
Dec. 31, 2014
|
Dec. 31, 2013
|
|
| Asset Retirement Obligation Disclosure [Abstract] | ||
| Restricted Cash and Cash Equivalents | $ 5,000,000 | $ 3,000,000 |
| Balance at beginning of period | 34,636,000 | 8,319,000 |
| Additions | 248,000 | 25,763,000 |
| Expenditures | (1,030,000) | 0 |
| Accretion expense | 791,000 | 554,000 |
| Balance at end of period | $ 34,645,000 | $ 34,636,000 |