Disclosures About Fair Value Measurements (Assets And Liabilities That Are Measured At Fair Value On A Recurring Basis) (Details) (USD $)	6 Months Ended
	Jun. 30, 2011
Assets, (Fair Value, Total)	$ 367,151,000
Liabilities, (Fair Value, Total)	3,282,392,000
Swap contract notional amount fixed rate of interest and variable LIBOR	470,000,000
Proceeds from termination of interest rate derivatives	26,100,000
Interest Rate Derivatives [Member]
Assets, (Fair Value, Total)	24,946,000	[1]
Interest Rate Derivatives [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, (Fair Value, Total)	24,946,000	[1]
Pioneer Southwest Credit Facility [Member]
Liabilities, (Fair Value, Total)	84,542,000
Pioneer Southwest Credit Facility [Member] | Significant Other Observable Inputs (Level 2) [Member]
Liabilities, (Fair Value, Total)	84,542,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Assets, (Fair Value, Total)	40,512,000
Liabilities, (Fair Value, Total)	3,013,767,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Trading Securities [Member]
Assets, (Fair Value, Total)	289,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Deferred Compensation Plan Assets [Member]
Assets, (Fair Value, Total)	40,223,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | 5.875% Senior Notes Due 2016 [Member]
Liabilities, (Fair Value, Total)	482,139,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | 6.65% Senior Notes Due 2017 [Member]
Liabilities, (Fair Value, Total)	529,972,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | 6.875% Senior Notes Due 2018 [Member]
Liabilities, (Fair Value, Total)	496,698,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | 7.50% Senior Notes Due 2020 [Member]
Liabilities, (Fair Value, Total)	512,158,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | 7.20% Senior Notes Due 2028 [Member]
Liabilities, (Fair Value, Total)	250,000,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | 2.875% Convertible Senior Notes Due 2038 [Member]
Liabilities, (Fair Value, Total)	742,800,000	[2]
Significant Other Observable Inputs (Level 2) [Member]
Assets, (Fair Value, Total)	326,639,000
Liabilities, (Fair Value, Total)	255,274,000
Significant Other Observable Inputs (Level 2) [Member] | Trading Securities [Member]
Assets, (Fair Value, Total)	30,149,000
Significant Other Observable Inputs (Level 2) [Member] | Commodity Derivatives [Member]
Assets, (Fair Value, Total)	271,544,000
Liabilities, (Fair Value, Total)	170,732,000
Significant Unobservable Inputs (Level 3) [Member]
Liabilities, (Fair Value, Total)	13,351,000
Significant Unobservable Inputs (Level 3) [Member] | Commodity Derivatives [Member]
Liabilities, (Fair Value, Total)	13,351,000
Trading Securities [Member]
Assets, (Fair Value, Total)	30,438,000
Commodity Derivatives [Member]
Assets, (Fair Value, Total)	271,544,000
Liabilities, (Fair Value, Total)	184,083,000
Deferred Compensation Plan Assets [Member]
Assets, (Fair Value, Total)	40,223,000
5.875% Senior Notes Due 2016 [Member]
Liabilities, (Fair Value, Total)	482,139,000
Senior notes, interest rate	5.875%
Debt instrument expiration date	2016
6.65% Senior Notes Due 2017 [Member]
Liabilities, (Fair Value, Total)	529,972,000
Senior notes, interest rate	6.65%
Debt instrument expiration date	2017
6.875% Senior Notes Due 2018 [Member]
Liabilities, (Fair Value, Total)	496,698,000
Senior notes, interest rate	6.875%
Debt instrument expiration date	2018
7.50% Senior Notes Due 2020 [Member]
Liabilities, (Fair Value, Total)	512,158,000
Senior notes, interest rate	7.50%
Debt instrument expiration date	2020
7.20% Senior Notes Due 2028 [Member]
Liabilities, (Fair Value, Total)	250,000,000
Senior notes, interest rate	7.20%
Debt instrument expiration date	2028
2.875% Convertible Senior Notes Due 2038 [Member]
Liabilities, (Fair Value, Total)	$ 742,800,000	[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.