Income Taxes (Schedule Of Components Of Income Tax Expense (Benefit)) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Loss Carryforwards [Line Items]
Net income (loss) before taxes	$ (894,944)	$ (89,037)	$ (111,998)
PRT tax current expense	9,172	20,667	31,796
PRT tax deferred benefit	(4,272)	(13,978)	(14,823)
PRT tax expense	4,900	6,689	16,973
Corporate current expense (benefit)	(106)	30	26
Corporate deferred expense	(59,483)	(277)	(11,358)
Deferred tax expense related to U.K. tax rate change			8,587
Corporate tax expense (benefit)	(59,589)	(247)	(2,745)
Income Tax Expense (Benefit)	(54,689)	6,442	14,228
Net Loss	(840,255)	(95,479)	(126,226)
U.K. [Member]
Operating Loss Carryforwards [Line Items]
Net income (loss) before taxes	(741,005)	(35,273)	(22,959)
PRT tax current expense	9,172	20,667	31,796
PRT tax deferred benefit	(4,272)	(13,978)	(14,823)
PRT tax expense	4,900	6,689	16,973
Corporate current expense (benefit)	(127)
Corporate deferred expense	(59,483)	(277)	(11,358)
Deferred tax expense related to U.K. tax rate change			8,587
Corporate tax expense (benefit)	(59,610)	(277)	(2,771)
Income Tax Expense (Benefit)	(54,710)	6,412	14,202
Net Loss	(686,295)	(41,685)	(37,161)
U.S. [Member]
Operating Loss Carryforwards [Line Items]
Net income (loss) before taxes	(137,440)	(44,591)	(91,383)
Net Loss	(137,440)	(44,591)	(91,383)
Other Countries [Member]
Operating Loss Carryforwards [Line Items]
Net income (loss) before taxes	(16,499)	(9,173)	2,344
Corporate current expense (benefit)	21	30	26
Corporate tax expense (benefit)	21	30	26
Income Tax Expense (Benefit)	21	30	26
Net Loss	$ (16,520)	$ (9,203)	$ 2,318