Income Taxes Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Valuation Allowance [Line Items]
Total income taxes	$ 15,806	$ 14,495	$ 280,760	$ (3,599)
Effective income tax rate	5.10%		26.70%
Federal statutory income tax rate			35.00%
Deferred	$ (15,806)	(14,495)	$ (280,760)	3,599
Other Comprehensive Income (Loss), Tax	11,500	$ 16,900	12,800	$ 1,200
Ceiling Test Write Downs From Decline in Commodity Prices [Member]
Valuation Allowance [Line Items]
Valuation allowance	$ 96,500		$ 96,500