Benefit Plans (Changes in projected benefit obligation) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Service cost	$ 150	$ 120	$ 105
Interest cost	120	110	103
Qualified Pension Plan [Member}
Projected benefit obligation, beginning of year	2,548	2,055
Service cost	139	113
Interest cost	107	100
Actuarial (gain) loss	(294)	296
Benefits paid	(63)	(57)
Acquisitions	0	41
Projected benefit obligation, end of year	2,437	2,548
Accumulated benefit obligation, end of year	2,062	2,166
Nonqualified Pension Plan [Member]
Projected benefit obligation, beginning of year	287	207
Service cost	11	7
Interest cost	12	10
Actuarial (gain) loss	2	70
Benefits paid	(8)	(7)
Projected benefit obligation, end of year	304	287
Accumulated benefit obligation, end of year	$ 215	$ 213