Employee Benefit Plans (Details) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 4	$ 4	$ 7	$ 8
Expected return on plan assets	(2)	(1)	(3)	(3)
Amortization of loss	1	0	2	1
Amortization of transition obligation	1	2	2	3
Net periodic cost	4	5	8	9
Expected contribution to postretirement benefit plan in current year	7		7
Total contribution to the plan during the period	$ 2		$ 4