Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 2	$ 3	$ 4
Interest cost	13	14	40	42
Expected return on plan assets	(19)	(19)	(58)	(57)
Net amortization	10	7	31	22
Net periodic benefit cost	5	4	16	11
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	2	4
Interest cost	4	7	12	21
Expected return on plan assets	(5)	(8)	(17)	(23)
Net amortization	(1)	1	(3)	2
Net periodic benefit cost	$ (2)	$ 1	$ (6)	$ 4