Employee Postretirement Benefits (Components of Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Recognized net actuarial loss	$ 109
Other Postretirement Benefit Plans, Defined Benefit [Member]
Service cost	14		14		14
Interest cost	41		44		47
Expected return on plan assets	0		0		0
Amortization of prior service cost and transition amount	1		3		2
Recognized net actuarial loss	0		1		0
Other	0		0		0
Net periodic benefit cost	56		62		63
Defined Benefit Pension [Member]
Service cost	57		56		68
Interest cost	307		309		310
Expected return on plan assets	(345)	[1]	(336)	[1]	(269)	[1]
Amortization of prior service cost and transition amount	3		2		3
Recognized net actuarial loss	94		99		111
Other	3		3		28
Net periodic benefit cost	$ 119		$ 133		$ 251

[1] The expected return on plan assets is determined by multiplying the fair value of plan assets at the remeasurement date, typically the prior year-end (adjusted for estimated current year cash benefit payments and contributions), by the expected long-term rate of return.