Basis Of Presentation (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010
Other Ownership Interests [Line Items]
Percentage of divest of subsidiaries capital stock				100.00%
Allowance for doubtful accounts	$ 1,021,000		$ 1,146,000
Materials and supplies inventories	321,900,000		297,900,000
Commodities	4,200,000		4,500,000
Inventory and supplies valuation reserve allowances	6,100,000		900,000
Inventory value classified as other noncurrent assets	44,200,000		60,800,000
Basis points added to LIBOR curves for determining credit-adjusted risk-free rate curve	162.5
Noncontrolling interest in consolidating subsidiaries	160,035,000		162,344,000
Equity interest in income of unconsolidated affiliate	6,981,000	298,000
Net income (loss) attributable to the noncontrolling interests	6,339,000	(4,790,000)
Amount of liabilities attributable to liability awards included in accounts payable	2,900,000		9,200,000
Allocated stock-based compensation expense	21,300,000	13,000,000
Unrecognized compensation expense	96,000,000
Restricted stock awards liability	44,300,000
Restricted stock awards unvested shares at balance sheet date	304,260		533,125
Pioneer South Africa [Member]
Other Ownership Interests [Line Items]
Net cash proceeds	52,000,000
EFS Midstream [Member]
Other Ownership Interests [Line Items]
Percent of interest owned	50.10%
General Partner Interest [Member]
Other Ownership Interests [Line Items]
Percent of interest owned	0.10%
Limited Partner Interest [Member]
Other Ownership Interests [Line Items]
Percent of interest owned	52.40%
Raton Shale Field [Member]
Other Ownership Interests [Line Items]
Carrying value of asset group	2,300,000,000
Barnett Shale Field [Member]
Other Ownership Interests [Line Items]
Carrying value of asset group	$ 511,700,000
Maximum [Member]
Other Ownership Interests [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period, years	three