Pension and Other Postretirement Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Pre-tax curtailment gain or settlement loss	$ 19
After-tax curtailment gain or settlement loss	12
Pension And Other Postretirement Footnote Text Details [Abstract]
Increase (decrease) to postretirement benefits liability adjustment pre-tax	(830)	129	558
Increase (decrease) to postretirement benefits liability adjustement after-tax	(539)	92	360
Pension Benefits [Member]
Change in benefit obligation [Abstract]
Benefit obligation, January 1	5,267	5,067
Service cost	3	3	2
Interest cost	181	198	228
(Gain) loss from past experience	(464)	283
Effect of plan ammendment	0	0
Benefits paid from plan assets	(262)	(256)
Benefits paid - other	(25)	(28)
Curtailment	0	0
Benefit obligation, December 31	4,700	5,267	5,067
Change in plan assets [Roll Forward]
Fair value of plan assets, January 1	3,665	3,298
Actual return on plan assets	488	370
Benefits paid	(262)	(256)
Contributions	198	253
Fair value of plan assets, December 31	4,089	3,665	3,298
Funded Status	(611)	(1,602)
Postretirement benefits liability adjustment included in AOCI table details [Abstract]
Unrecognized net gain (loss)	(1,696)	(2,450)
Unrecognized prior service cost	(5)	(5)
Postretirement benefits liabilty adjustment	(1,701)	(2,455)
Components of net pension cost and other postretirement benefits cost tables detail [Abstract]
Service cost	3	3	2
Interest cost	181	198	228
Expected long-term return on plan assets	(272)	(270)	(267)
Amortization of net loss from past experience	74	58	38
Settlement loss	0	6	0
Net pension cost	(14)	(5)	1
Pension And Other Postretirement Footnote Text Details [Abstract]
Defined Benefit Plan Accumulated Benefit Obligations	4,700	5,300
Expected minimum required funding contributions next year	100
Expected pre-tax gains (losses) related to amortization of prior experience	(57)
Weighted average amortization period for amortization of past experience	28 years
Other Postretirement Benefits [Member]
Change in benefit obligation [Abstract]
Benefit obligation, January 1	442	452
Service cost	1	2	2
Interest cost	12	16	20
(Gain) loss from past experience	(37)	(2)
Effect of plan ammendment	(57)	0
Benefits paid from plan assets	(3)	(3)
Benefits paid - other	(28)	(23)
Curtailment	(7)	0
Benefit obligation, December 31	323	442	452
Change in plan assets [Roll Forward]
Fair value of plan assets, January 1	20	22
Actual return on plan assets	(1)	1
Benefits paid	(3)	(3)
Contributions	0	0
Fair value of plan assets, December 31	16	20	22
Funded Status	(307)	(422)
Postretirement benefits liability adjustment included in AOCI table details [Abstract]
Unrecognized net gain (loss)	14	(28)
Unrecognized prior service cost	57	23
Postretirement benefits liabilty adjustment	71	(5)
Components of net pension cost and other postretirement benefits cost tables detail [Abstract]
Service cost	1	2	2
Interest cost	12	16	20
Expected long-term return on plan assets	(1)	(1)	(1)
Amortization of prior service cost	(4)	(12)	(16)
Curtailment (gain) loss	(19)	0	0
Net pension cost	(11)	5	5
Pension And Other Postretirement Footnote Text Details [Abstract]
Expected pre-tax gains (losses) related to amortization of net prior service cost
Results of a 1% increase or decrease in healthcare benefits estimate range table details [Abstract]
Effect of increase on total service and interest cost	0
Effect of decrease on total service and interest cost	0
Effect of increase on postretirement benefit obligation	3
Effect of decrease on postretirement benefit obligation	0
Retiree Health Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (decrease) to shareholders' equity resulting from plan ammendments	37
Pension And Other Postretirement Footnote Text Details [Abstract]
Defined Benefit Plan Accumulated Benefit Obligations	190	294
Expected pre-tax gains (losses) related to amortization of prior experience	0
Weighted average amortization period for amortization of past experience	28 years
Estimated rate of future increases in the per capita cost of health care benefits	7.00%
Estimated decrease in rate per year of future increases in the per capita cost of health care benefits	decreasing by 0.5% per year
Estimated rate of future increases in the per capita cost of health care benefits in 2018 and beyond	5.00%
Year that estimated rate of future cost of health care is realized	2018
Retiree Life Insurance Benefits [Member]
Pension And Other Postretirement Footnote Text Details [Abstract]
Defined Benefit Plan Accumulated Benefit Obligations	$ 133	$ 148