Retirement and Post-retirement Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Defined benefit plans
Postretirement and Other Benefit Plans Disclosure
Employer contributions	$ 1	$ 0	$ 2	$ 5
Pension Benefit
Net periodic benefit costs:
Service cost	2	2	4	4
Interest cost	4	5	8	10
Expected return on plan assets	(6)	(7)	(12)	(14)
Recognized actuarial loss	3	2	6	4
Settlement loss	2		2
Net periodic benefit cost	5	2	8	4
Post-retirement Benefit
Net periodic benefit costs:
Service cost	5	7	10	14
Interest cost	10	10	20	20
Recognized actuarial loss	6	7	11	14
Net periodic benefit cost	$ 21	$ 24	$ 41	$ 48