Benefit Plans (Summary of the Components of Net Periodic Benefit Cost Recognized for Pension Plans) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 138	$ 150	$ 120
Interest cost	140	120	110
Estimated return on plan assets	(296)	(257)	(200)
Net amortization and other	17	91	76
Net periodic benefit cost	(1)	104	106
Net actuarial loss (gain)	532	(535)	270
Net amortization	(17)	(91)	(76)
Net amount recognized in OCI	515	(626)	194
Total net periodic pension (income) costs recognized in total comprehensive income	514	(522)	300
Qualified Pension Plan [Member}
Defined Benefit Plan Disclosure [Line Items]
Service cost	128	139
Interest cost	124	107
Nonqualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	10	11
Interest cost	$ 16	$ 12