Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate percentage	12.10%			35.80%	24.90%	36.40%
Deferred tax assets valuation allowance	$ 66,600				$ 66,600
Income Tax Expense (Benefit)	(33,305)			$ 16,504	(149,045)	$ 36,675
Changes in Future Income Tax Expense Estimates on Future Cash Flows Related to Proved Oil and Gas Reserves	$ 33,300	$ 82,700	$ 24,300		$ 140,300