Pension and Other Postretirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Benefits [Member]
Components Of Net Periodic Cost Details [Abstract]
Service cost	$ 8	$ 10	$ 16	$ 20
Interest cost	59	52	118	104
Expected return on plan assets	(66)	(67)	(132)	(134)
Amortization of actuarial losses (gains)	16	22	32	44
Net periodic cost	17	17	34	34
Postretirement Benefits [Member]
Components Of Net Periodic Cost Details [Abstract]
Service cost	0	0	0	0
Interest cost	6	6	12	12
Expected return on plan assets	0	0	0	0
Amortization of actuarial losses (gains)	(5)	(4)	(10)	(8)
Net periodic cost	$ 1	$ 2	$ 2	$ 4