Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income:
Net actuarial loss (gain)	$ (1)		$ 0
Amortization of net prior service credit	27	[1]	31	[1]
Contributions [Abstract]
Contribution of common stock to a benefit plan	130	[2]
Pension Benefits [Member]
Components of Net Periodic Benefit Costs:
Service cost	51		48
Interest cost	115		118
Expected return on plan assets	(129)		(127)
Recognized net actuarial loss	27		17
Amortization of prior service credit	(6)		(6)
Recognized settlement loss	16		30
Defined Benefit Plan, Net Periodic Benefit Cost	74		80
Net Periodic Benefit Plan, Defined Benefit and Contribution Plans	90		96
Defined Contribution Plan, Cost Recognized	16		16
Total net periodic benefit cost	74		80
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income:
Net actuarial loss (gain)	(1)		0
Amortization of net prior service credit	6		6
Amortization of net actuarial losses	(43)		(47)
Total Recognized in Other Comprehensive Income	(38)	[3]	(41)	[3]
Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income	52		55
Contributions [Abstract]
Contributions by employer	79
Stock Issued During Period, Shares, Employee Benefit Plan	15.4
Contribution of common stock to a benefit plan	130
Anticipated additional contributions	351
Anticipated cash contributions	430
Anticipated total contributions	560
Retiree Health [Member]
Components of Net Periodic Benefit Costs:
Service cost	2		2
Interest cost	11		12
Expected return on plan assets	0		0
Recognized net actuarial loss	0		0
Amortization of prior service credit	(10)		(10)
Recognized settlement loss	0		0
Defined Benefit Plan, Net Periodic Benefit Cost	3		4
Net Periodic Benefit Plan, Defined Benefit and Contribution Plans	3		4
Defined Contribution Plan, Cost Recognized	0		0
Total net periodic benefit cost	3		4
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income:
Net actuarial loss (gain)	0		0
Amortization of net prior service credit	10		10
Amortization of net actuarial losses	0		0
Total Recognized in Other Comprehensive Income	10	[3]	10	[3]
Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income	13		14
Contributions [Abstract]
Contributions by employer	12
Anticipated additional contributions	68
Anticipated cash contributions	$ 80

[1] (2) Reclassified to Total Net Periodic Benefit Cost - refer to Note 13 - Employee Benefit Plans for additional information.

[2] (4)Refer to Note 13 - Employee Benefit Plans for additional information.

[3] Amounts represent the pre-tax effect included within Other comprehensive income. Refer to Note 15 - Comprehensive Income for related tax effects and the after-tax amounts.