Certain Employee Benefit and Stock Based Compensation Plans (Net Periodic Pension and Postretirement Benefits Costs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 29	$ 25	$ 57	$ 51
Interest cost	43	48	85	96
Expected return on plan assets	(72)	(71)	(144)	(142)
Amortization of prior service credit	(2)	(2)	(4)	(4)
Amortization of actuarial losses	21	22	43	44
Net periodic cost/(benefit)	19	22	37	45
Nonqualified Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	2	2
Interest cost	3	4	6	7
Amortization of actuarial losses	2	1	4	3
Net periodic cost/(benefit)	6	6	12	12
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	3	3
Interest cost	4	4	8	8
Amortization of prior service credit	(1)	(1)	(2)	(2)
Amortization of actuarial losses		(1)
Net periodic cost/(benefit)	$ 5	$ 4	$ 9	$ 9