Divestitures, Assets Held for Sale, and Acquisitions Divestitures and Assets Held for Sale (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from the sale of oil and gas properties		$ 744,333	$ 1,206
Net gain (loss) on divestiture activity		37,463	(69,021)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		118,940	(542,085)
Impairment of Proved Oil and Gas Properties		$ 0	269,785
Assets Held-for-sale Reasonably Certain Period for Sale		1 year
Disposal Group, Including Discontinued Operation, Assets, Current		$ 455,943		$ 372,621
Asset retirement obligation associated with oil and gas properties held for sale		16,056		$ 26,241
Abandonment and impairment of unproved properties		0	2,311
Non-Operated Eagle Ford Divestiture 2017 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from the sale of oil and gas properties		747,400
Net gain (loss) on divestiture activity		398,100
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	[1]	24,324	(286,399)
Impairment of Proved Oil and Gas Properties			269,600
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Divide County Divestiture 2017 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	[2]	(335,561)	(16,813)
Impairment of Proved Oil and Gas Properties		$ 359,600
Abandonment and impairment of unproved properties			$ 1,600

[1] Income (loss) before income taxes reflects oil, gas, and NGL production revenue, less oil, gas, and NGL production expense and depletion, depreciation, amortization, and asset retirement obligation liability accretion. Additionally, income (loss) before income taxes included impairment of proved properties expense of approximately $269.6 million for the three months ended March 31, 2016.

[2] Loss before income taxes reflects oil, gas, and NGL production revenue less oil, gas, and NGL production expense and depletion, depreciation, amortization, and asset retirement obligation liability accretion. Additionally, loss before income taxes for the three months ended March 31, 2017, included the $359.6 million write-down on these assets held for sale as discussed above, and loss before income taxes for the three months ended March 31, 2016, included $1.6 million of unproved property impairments.