Pension and Other Postretirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension And Other Postretirement Footnote Text Details [Abstract]
Increase (decrease) to postretirement benefits liability adjustment pre-tax	$ (19)
Increase (decrease) to postretirement benefits liability adjustement after-tax	(12)	(40)
Pension Benefits [Member]
Components of net pension cost and other postretirement benefits cost tables detail [Abstract]
Service cost	0	1
Interest cost	51	45
Expected long-term return on plan assets	(66)	(68)
Amortization of net loss from past experience	14	19
Amortization of prior service cost	0	0
Settlement loss	6	0
Curtailment (gain) loss	0	0
Net pension cost	5	(3)
Pension And Other Postretirement Footnote Text Details [Abstract]
Required domestic pension plan contributions	113
Expected plan contributions during remainder of current fiscal year	0
Other Postretirement Benefits [Member]
Components of net pension cost and other postretirement benefits cost tables detail [Abstract]
Service cost	0	0
Interest cost	3	3
Expected long-term return on plan assets	0	0
Amortization of net loss from past experience	0	0
Amortization of prior service cost	(1)	(2)
Settlement loss	0	0
Curtailment (gain) loss	0	(19)
Net pension cost	2	(18)
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]
Increase (decrease) to postretirement benefits liability adjustement after-tax	$ (57)