Employee Benefit Plans (Details) - Components of Pension and Other Retirement Benefit Costs - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7	$ 6	$ 21	$ 18
Interest cost	11	12	34	35
Expected return on plan assets	(16)	(16)	(49)	(48)
Net amortization of prior service cost (credit)	(1)	(1)	(2)	(2)
Recognized actuarial loss	8	5	23	16
Net periodic pension benefit cost	9	6	27	19
Health and Welfare Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	1	2
Interest cost	4	4	10	11
Expected return on plan assets	(1)	(2)	(5)	(5)
Net amortization of prior service cost (credit)	(1)	(1)	(2)	(2)
Recognized actuarial loss	1	1	4	4
Net periodic pension benefit cost	$ 3	$ 3	$ 8	$ 10