Employee Benefit Plans (Net Periodic Defined Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Postretirement Benefit Plan [Member]
Interest cost	$ 1	$ 1	$ 2	$ 2
Expected return on plan assets	(1)	(1)	(2)	(2)
Amortization of transition obligation	1	1	2	2
Amortization of net loss	1	1	1	1
Net periodic benefit cost	2	2	3	3
Qualified Defined Benefit Pension Plan [Member] | Pension Plans, Defined Benefit [Member]
Service cost	8	8	16	16
Interest cost	21	19	40	38
Expected return on plan assets	(28)	(29)	(56)	(58)
Amortization of prior service cost	1	1	2	2
Amortization of net loss	13	9	26	18
Net periodic benefit cost	15	8	28	16
Non-Qualified Defined Benefit Pension Plan [Member] | Pension Plans, Defined Benefit [Member]
Service cost	1	1	2	2
Interest cost	3	3	5	5
Amortization of prior service cost	(1)	(1)	(1)	(1)
Amortization of net loss	2	1	4	2
Net periodic benefit cost	$ 5	$ 4	$ 10	$ 8