Retirement and Post-retirement Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Defined benefit pension plans
Postretirement and Other Benefit Plans Disclosure
Employer contributions	$ 1	$ 5
Pension Benefit
Net periodic benefit costs:
Service cost	2	2
Interest cost	4	5
Expected return on plan assets	(6)	(7)
Recognized actuarial loss	3	2
Net periodic benefit cost	3	2
Postretirement Benefit
Net periodic benefit costs:
Service cost	5	7
Interest cost	10	10
Recognized actuarial loss	5	7
Net periodic benefit cost	$ 20	$ 24