Certain Employee Benefit and Stock Based Compensation Plans (Net Periodic Pension and Postretirement Benefits Costs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 26	$ 26	$ 53	$ 51
Interest cost	45	47	89	94
Expected return on plan assets	(74)	(72)	(148)	(144)
Amortization of prior service cost/(credit)	(2)	(2)	(4)	(4)
Amortization of actuarial losses	8		15
Net periodic cost/(benefit)	3	(1)	5	(3)
Nonqualified Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1	2
Interest cost	3	3	6	6
Amortization of actuarial losses	1	1	3	2
Net periodic cost/(benefit)	5	5	10	10
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	3	2
Interest cost	3	4	7	8
Net periodic cost/(benefit)	$ 5	$ 5	$ 10	$ 10