Employee Benefit Plans Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 1
Interest cost	13	14
Expected return on plan assets	(19)	(19)
Net amortization	10	8
Net periodic benefit cost	5	4
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	4	7
Expected return on plan assets	(6)	(8)
Net amortization	(1)	1
Net periodic benefit cost	$ (2)	$ 1