Pension and Other Postretirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Pension Benefits [Member]	Jun. 30, 2012 Pension Benefits [Member]	Jun. 30, 2013 Pension Benefits [Member]	Jun. 30, 2012 Pension Benefits [Member]	Jun. 30, 2013 Other Postretirement Benefits [Member]	Jun. 30, 2012 Other Postretirement Benefits [Member]	Jun. 30, 2013 Other Postretirement Benefits [Member]	Jun. 30, 2012 Other Postretirement Benefits [Member]	Mar. 31, 2013 Retiree Health Benefits [Member]	Jun. 30, 2013 Retiree Life Insurance Benefits [Member]	Dec. 31, 2012 Retiree Life Insurance Benefits [Member]	Dec. 31, 2012 Retiree Life Insurance Benefits [Member] Scenario, Previously Reported [Member]
Change in benefit obligation [Abstract]
Service cost					$ 0	$ 0	$ 1	$ 1	$ 0	$ 1	$ 0	$ 1
Interest cost					46	50	91	99	3	4	6	8
Amendments													(57)
Components of net pension cost and other postretirement benefits cost tables detail [Abstract]
Service cost					0	0	1	1	0	1	0	1
Interest cost					46	50	91	99	3	4	6	8
Expected long-term return on plan assets					(68)	(67)	(136)	(134)	0	0	0	0
Amortization of net loss from past experience					18	15	37	30	0	0	0	0
Amortization of prior service cost					0	0	0	0	(1)	(3)	(3)	(6)
Curtailment gain					0	0	0	0	0	0	(19)	0
Settlement loss					0	0	0	6	0	0	0	0
Net pension cost					(4)	(2)	(7)	2	2	2	(16)	3
Pension And Other Postretirement Footnote Text Details [Abstract]
Increase (decrease) to postretirement benefits liability adjustment pre-tax	(33)	(36)	(94)	(54)
Increase (decrease) to postretirement benefits liability adjustment after-tax	(21)	(25)	(61)	(36)
Expected pre-tax gains (losses) related to amortization of net prior service cost														4		9
Weighted Average Remaining amortization period for prior service costs															2 years 6 months
Average life expectancy of frozen plan participants														25 years
Domestic qualified pension plan contributions			28
Expected plan contributions during remainder of current fiscal year	$ 222		$ 222