Benefit Plans (Summary of the components of net periodic benefit cost recognized for pension plans) (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
Qualified Pension Plan [Member}
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 32	$ 37	$ 65	$ 74
Interest cost	31	27	62	54
Estimated return on plan assets	(74)	(64)	(148)	(128)
Amortization and other	1	20	1	40
Net periodic benefit cost	(10)	20	(20)	40
Nonqualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	3	6	6
Interest cost	3	4	7	7
Estimated return on plan assets	0	0	0	0
Amortization and other	3	3	6	6
Net periodic benefit cost	$ 9	$ 10	$ 19	$ 19