Acquisitions and Divestitures (Narrative) (Details) - Long Lived Assets Held-for-sale, Name [Domain] $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2014
Acquisitions and Divestitures [Line Items]
Gain (loss) on disposition of assets, net		$ 2,000	$ 4,000	$ 3,000	$ 10,000
Idle Rig Expense	[1]	28,000	0	51,000	0
Proceeds from Sale of Productive Assets				7,000	369,000
Impairment of oil and gas properties		0	$ 0	138,000	0
Sendero [Member]
Acquisitions and Divestitures [Line Items]
Gain (loss) on disposition of assets, net					1,000
Proceeds from Divestiture of Interest in Consolidated Subsidiaries					31,000
Idle Rig Expense		$ 10,000		$ 20,000
Gaines Dawson [Member]
Acquisitions and Divestitures [Line Items]
Gain (loss) on disposition of assets, net					2,000
Proceeds from Sale of Productive Assets					$ 72,000
Lease Contract through Year 2 [Member]
Acquisitions and Divestitures [Line Items]
Drilling rigs leased							12
Lease Contract for Year 3 [Member]
Acquisitions and Divestitures [Line Items]
Drilling rigs leased							8
Discontinued Operations [Member] | Hugoton field [Member]
Acquisitions and Divestitures [Line Items]
Proceeds from Sale of Productive Assets						$ 328,000
Discontinued Operations [Member] | Pioneer Alaska [Member]
Acquisitions and Divestitures [Line Items]
Proceeds from Sale of Productive Assets						267,000
Discontinued Operations [Member] | Barnett Shale Field [Member]
Acquisitions and Divestitures [Line Items]
Proceeds from Sale of Productive Assets						$ 150,000

[1] Primarily represents expenses attributable to idle drilling rig fees, which are not chargeable to joint operations.