Employee Benefit Plans (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Proportion of other postretirement benefit plan assets subjected to income tax		40.00%
Pension plan assets equity securities target allocation range,minimum		54.00%
Pension plan assets equity securities target allocation range,maximum		66.00%
Fixed income commingled fund's maximum allocation to BBB rated securities		10.00%
Fixed income commingled fund's target approximate duration in years		20
Maturities of investments within cash management fund		1 year
Employees Benefit Plans (Textuals) [Abstract]
Plan assets market related value		may be no more than 110 percent or less than 90 percent of the fair value of plan assets at the beginning of the year
Health care cost trend rate assumed for next fiscal year	8.20%
Direction and pattern of change for assumed health care cost trend rate		decreases
Ultimate health care cost trend rate		5.00%
Year that rate reaches ultimate trend rate		2021
Pension plan assets fixed income securities and cash management target allocation range, minimum		36.00%
Pension plan assets fixed income securities and cash management target allocation range, maximum		44.00%
Maximum percentage of total stock portfolio invested in the common stock of any one corporation		5.00%
Maximum percentage of portfolio invested in fixed income securities of any one issuer with exception of bond index funds and U. S. government guaranteed and agency securities		5.00%
Number of active investment managers managing pension plans funds		9
Number of passive investment managers managing pension plans funds		1
Number of active investment managers managing other postretirement benefit plans funds		5
Each investment manager responsibility to manage the pension plans' funds, minimum		1.00%
Each investment manager responsibility to manage the pension plans' funds, maximum		16.00%
Required value of collateralization for loaned securities		equaled at least 102 percent of the fair value of the loaned securities plus accrued interest
Pension plans loaned securities fair values			$ 116
Other postretirement benefit plans loaned securities fair values			17
Employer's contributions charged to expense under defined contribution plans		28	26	25
Defined contribution plan matching contributions included in income (loss) from discontinued operations related to WPX employees		5	5	5
U. S. Equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets equity securities target allocation range,minimum		37.00%
Pension plan assets equity securities target allocation range,maximum		45.00%
International Equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets equity securities target allocation range,minimum		17.00%
Pension plan assets equity securities target allocation range,maximum		21.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation actuarial loss		(143)	(108)
Approximate period of the net actuarial gain (loss) amortized over the participants' average remaining future years service		13
Fair value of securities held as collateral and obligation to return collateral			120
Expected tax-qualified pension plans contribution, approximate	70
Expected nonqualified pension plans contribution, approximate	9
Expected total plans contribution, approximate	79
Weighted average duration of fixed income security portfolio (in years)		5.6	5.6
Amounts related to WPX's net periodic benefit expense recorded in income (loss) from discontinued operations		8	7	7
Curtailment gain included in actuarial loss within benefit obligation rollforward		4
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation actuarial loss		(48)	(30)
Approximate period of the net actuarial gain (loss) amortized over the participants' average remaining future years service		10
Fair value of securities held as collateral and obligation to return collateral			17
Net regulatory liabilities		34	23
Expected total plans contribution, approximate	15
Weighted average duration of fixed income security portfolio (in years)		4.8	4.8
Amounts related to WPX's net periodic benefit expense recorded in income (loss) from discontinued operations		1	1	1
Curtailment gain included in actuarial loss within benefit obligation rollforward		1
Net regulatory assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)		39	10	(14)
Prior service credit		1	1	11
Amortization of prior service credit for regulatory assets		7	9	7
Amortization of net actuarial (gain) loss for regulatory assets		$ 2	$ 2	$ 3