Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Computed expected tax expense (benefit)	$ (720,923)	$ 154,766	$ 35,265
Increase (decrease) resulting from State and foreign income taxes	(6,353)	8,467	(852)
Increase (decrease) resulting other	10,861	(1,834)	(14,015)
Income Tax Expense (Benefit), Total	(252,020)	$ 161,399	55,272
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount	$ 464,395		$ 34,874