Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 23, 2013
Deferred tax liabilities [Abstract]
Marketable securities	$ 0	$ 0	$ 28
Hedge contracts	8,114	0	0
Deferred Tax Liabilities, Other	4,458	3,152	0
Total deferred tax liabilities	12,572	3,152	28
Deferred tax assets [Abstract]
U.S. full cost pool	3,352	11,725	13,837
Deferred tax assets additional full cost pool	0	4,081	3,720
Deferred Tax Assets, Capital Loss Carryforwards	12,325	0	0
Depletion carryforward	4,936	4,743	4,930
U.S. net operating loss carryforward	50,941	49,667	59,362
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	0	5,736	4,196
Alternative minimum tax credit	1,104	1,369	422
Hedge contracts	0	1,397	2,231
Other	0	0	1,042
Total deferred tax assets	72,658	78,718	89,740
Valuation allowance for deferred tax assets	(60,086)	(75,566)	(89,712)
Net deferred tax assets	12,572	3,152	28
Net deferred tax	0	0	0
Current [Abstract]
Federal	(276)	632	310
State	(11)	68	0
Current provision (benefit) for income taxes	(287)	700	310
Deferred [Abstract]
Federal	0	0	0
Foreign	0	0	0
Deferred provision (benefit) for income taxes	0	0	0
Operating Loss Carryforwards [Line Items]
Income taxes paid				391
Tax Adjustments, Settlements, and Unusual Provisions		81
Reconciliation of income tax computed at U.S federal statutory tax rates [Abstract]
Tax (expense) benefit at U.S. statutory rates (35%)	(22,044)	(13,771)	6,468
(Increase) decrease in deferred tax asset valuation allowance	15,480	14,146	(6,231)
Rate differential for non US income	(39)	(574)	(1,533)
State income taxes	0	(47)	0
Accrual of prior year federal taxes (2009)	287	(81)	(310)
Permanent differences	(950)	(743)	(732)
Return to provision estimate revision	4,562	0	0
Tax benefit related to the sale of Canadian subsidary	3,501	0	0
Increase in asset for partnership distributions	0	0	1,945
Other	(510)	370	83
Income tax (expense) benefit	287	(700)	(310)
U.S statutory rate (in hundredths)	35.00%
Reduction in deferred tax assets	(6,000)
Tax adjustment assessed		619	310
U.S. Tax [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 145,500
Expiration dates of operating loss carryforwards	Dec. 31, 2034