Income Taxes (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended	3 Months Ended
	Dec. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Operating Loss Carryforwards [Line Items]
U.S. statutory rate		35.00%
Foreign statutory rate	62.00%	50.00%
Deferred tax expense (benefit)		$ (11,137)	$ 1,969
Ring Fence Corporation Tax [Member]
Operating Loss Carryforwards [Line Items]
Foreign statutory rate	30.00%
Supplementary Charge [Member]
Operating Loss Carryforwards [Line Items]
Foreign statutory rate	32.00%	20.00%
Deferred tax expense (benefit)		11,400
Petroleum Revenue Tax [Member]
Operating Loss Carryforwards [Line Items]
Foreign statutory rate		50.00%
Deferred tax expense (benefit)		$ (7,900)
PRT Rate Beginning On January 1, 2016 [Member]
Operating Loss Carryforwards [Line Items]
Foreign statutory rate		35.00%