Employee Pension and Other Postretirement Benefits (Details 2) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 23	$ 25
Interest cost	26	27
Expected return on plan assets	(60)	(54)
Amortization of prior service cost	(4)	(4)
Recognized net actuarial loss	19	27
Total net periodic benefit cost	4	21
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	2	2
Interest cost	3	3
Expected return on plan assets	(5)	(5)
Amortization of prior service cost	(2)	(2)
Recognized net actuarial loss	2	1
Total net periodic benefit cost	0	(1)
Superannuation, SERP and ESBP
Components of net periodic benefit cost:
Service cost	1	0
Interest cost	0	0
Expected return on plan assets	0	0
Amortization of prior service cost	0	0
Recognized net actuarial loss	1	1
Total net periodic benefit cost	$ 2	$ 1