Other Postretirement Benefits (Funded Status) (Details) (Other Postretirement Benefits [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other Postretirement Benefits [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Projected benefit obligation at beginning of year	$ 1,642	$ 1,697	$ 1,702
Service cost		24	22
Interest cost on accumulated postretirement benefit obligation	83	91	95
Net actuarial loss/(gain)	109	(68)	(14)
Benefits paid and administrative expenses	(144)	(138)	(141)
Participant contributions	33	29	26
Medicare prescription benefit	8	7	7
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	1,756	1,642	1,697
Fair value of plan assets at beginning of year	942	866	737
Actual return on plan assets	20	89	153
Employer contributions	84	96	86
Benefits paid	(132)	(138)	(136)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	947	942	866
FUNDED STATUS	(809)	(700)	(831)
Unrecognized net loss	563	483	646
Unrecognized prior service costs	(1)	(10)	(23)
Unrecognized net transition liability at January 1, 1993	$ 4	$ 7	$ 11