Employee Benefit Plans (Net Periodic Costs (Components of Net Periodic Benefit Costs) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Amortization of actuarial gain/(loss)	$ (38,000,000)	$ (4,000,000)	$ (103,000,000)
Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	107,000,000	103,000,000	113,000,000
Interest cost	177,000,000	187,000,000	170,000,000
Expected return on plan assets	(297,000,000)	(289,000,000)	(288,000,000)
Amortization of prior service cost/(credit)	(9,000,000)	(8,000,000)	(8,000,000)
Amortization of actuarial losses	31,000,000		87,000,000
Net periodic cost/(benefit)	9,000,000	(7,000,000)	74,000,000
Current year prior service cost/(credit)		(7,000,000)
Amortization of prior service (cost)/credit	9,000,000	8,000,000	8,000,000
Current year actuarial loss/(gain)	152,000,000	434,000,000	(784,000,000)
Amortization of actuarial gain/(loss)	(31,000,000)		(87,000,000)
Total recognized in OCI	130,000,000	435,000,000	(863,000,000)
Total amount recognized in net periodic cost and OCI	139,000,000	428,000,000	(789,000,000)
Nonqualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	3,000,000	3,000,000	3,000,000
Interest cost	11,000,000	12,000,000	12,000,000
Amortization of actuarial losses	7,000,000	4,000,000	8,000,000
Settlement (gain)/loss			7,000,000
Net periodic cost/(benefit)	21,000,000	19,000,000	30,000,000
Current year actuarial loss/(gain)	(10,000,000)	40,000,000	(26,000,000)
Amortization of actuarial gain/(loss)	(7,000,000)	(4,000,000)	(15,000,000)
Total recognized in OCI	(17,000,000)	36,000,000	(41,000,000)
Total amount recognized in net periodic cost and OCI	4,000,000	55,000,000	(11,000,000)
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	5,000,000	5,000,000	6,000,000
Interest cost	15,000,000	16,000,000	14,000,000
Amortization of prior service cost/(credit)	(1,000,000)	(2,000,000)	(3,000,000)
Settlement (gain)/loss			1,000,000
Net periodic cost/(benefit)	19,000,000	19,000,000	18,000,000
Amortization of prior service (cost)/credit	1,000,000	2,000,000	3,000,000
Current year actuarial loss/(gain)	(9,000,000)	4,000,000	(9,000,000)
Amortization of actuarial gain/(loss)			(1,000,000)
Total recognized in OCI	(8,000,000)	6,000,000	(7,000,000)
Total amount recognized in net periodic cost and OCI	$ 11,000,000	$ 25,000,000	$ 11,000,000