Disclosures About Fair Value Measurements (Fair Values Of The Company's Financial Instruments) (Details) (USD $)	6 Months Ended
	Jun. 30, 2011		Dec. 31, 2010
Liabilities
Proceeds from termination of interest rate derivatives	$ 26,100,000
Interest Rate Derivatives [Member]
Assets
Carrying Value	24,946,000	[1]	18,256,000	[1]
Fair Value	24,946,000	[1]	18,256,000	[1]
Liabilities
Carrying Value			704,000
Fair Value			704,000
Pioneer Southwest Credit Facility [Member]
Liabilities
Carrying Value	87,000,000		81,200,000
Fair Value	84,542,000		77,241,000
Pioneer Credit Facility [Member]
Liabilities
Carrying Value			49,000,000
Fair Value			58,382,000
Trading Securities [Member]
Assets
Carrying Value	30,438,000		467,000
Fair Value	30,438,000		467,000
Commodity Derivatives [Member]
Assets
Carrying Value	271,544,000		304,434,000
Fair Value	271,544,000		304,434,000
Liabilities
Carrying Value	184,083,000		136,867,000
Fair Value	184,083,000		136,867,000
Deferred Compensation Plan Assets [Member]
Assets
Carrying Value	40,223,000		36,162,000
Fair Value	40,223,000		36,162,000
5.875% Senior Notes Due 2016 [Member]
Liabilities
Carrying Value	401,037,000		396,880,000
Fair Value	482,139,000		475,194,000
Senior notes, interest rate	5.875%
Debt instrument expiration date	2016
6.65% Senior Notes Due 2017 [Member]
Liabilities
Carrying Value	484,114,000		484,046,000
Fair Value	529,972,000		516,632,000
Senior notes, interest rate	6.65%
Debt instrument expiration date	2017
6.875% Senior Notes Due 2018 [Member]
Liabilities
Carrying Value	449,209,000		449,192,000
Fair Value	496,698,000		480,969,000
Senior notes, interest rate	6.875%
Debt instrument expiration date	2018
7.50% Senior Notes Due 2020 [Member]
Liabilities
Carrying Value	446,572,000		446,433,000
Fair Value	512,158,000		494,145,000
Senior notes, interest rate	7.50%
Debt instrument expiration date	2020
7.20% Senior Notes Due 2028 [Member]
Liabilities
Carrying Value	249,927,000		249,925,000
Fair Value	250,000,000		259,350,000
Senior notes, interest rate	7.20%
Debt instrument expiration date	2028
2.875% Convertible Senior Notes Due 2038 [Member]
Liabilities
Carrying Value	453,119,000	[2]	444,994,000	[2]
Fair Value	$ 742,800,000	[2]	$ 728,400,000	[2]
Senior notes, interest rate	2.875%
Debt instrument expiration date	2038

[1] Subsequent to June 30, 2011, the Company terminated the interest rate derivatives shown in the table above and received $26.1 million of proceeds. See Note G for additional information about the Company's interest rate derivatives.

[2] The fair value of the 2.875% senior convertible notes includes the fair value of the conversion privilege.