Asset Divestitures (Details) (USD $)	12 Months Ended			1 Months Ended		12 Months Ended	1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Feb. 28, 2011 Pioneer Tunisia [Member]	Jun. 30, 2010 EFS Midstream [Member] years	Dec. 31, 2010 EFS Midstream [Member]	Jun. 30, 2010 Eagle Ford Shale [Member]	Dec. 31, 2011 Eagle Ford Shale [Member]	Dec. 31, 2010 Uinta/Piceance [Member]
Asset Divestitures [Line Items]
Net proceeds from asset divestitures	$ 819,000,000	$ 313,800,000	$ 51,600,000
Gain (loss) on disposition of assets in continuing operations	(3,600,000)	19,100,000	(774,000)				6,000,000		17,300,000
Gains from the disposition of discontinued operations	645,200,000	17,500,000
Cash proceeds from sale of subsidiaries, net				853,600,000
Joint venture percentage							45.00%
Proceeds from disposition of assets, net	819,044,000	313,780,000	51,600,000			1,100,000	212,000,000		11,800,000
Payments for exploration, drilling and completion costs, percent								75.00%
Maximum payments for exploration, drilling and completion costs								886,800,000
Net loss on sale of other asses, before tax	5,100,000	4,200,000
Deferred gain on sale of EFS midstream					$ 46,200,000
EFS midstream deferred gain amortization period, years					20