Employee Benefit Plans Employee Benefit Plans - Net Periodic Benefit Cost (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5	$ 6	$ 7
Interest cost	57	54	61
Expected return on plan assets	(76)	(74)	(74)
Net amortization	29	48	34
Net periodic benefit cost	15	34	28
Other Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	9	7
Interest cost	28	25	28
Expected return on plan assets	(31)	(30)	(30)
Net amortization	2	8	4
Net periodic benefit cost	$ 5	$ 12	$ 9