Employee Pension and Other Postretirement Benefits (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 25	$ 21
Interest cost	27	27
Expected return on plan assets	(54)	(48)
Amortization of prior service cost	(4)	0
Recognized net actuarial loss	27	14
Total net periodic benefit cost	21	14
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	2	3
Interest cost	3	3
Expected return on plan assets	(5)	(4)
Amortization of prior service cost	(2)	0
Recognized net actuarial loss	1	0
Total net periodic benefit cost	(1)	2
Superannuation, SERP and ESBP
Components of net periodic benefit cost:
Service cost	0	1
Interest cost	0	1
Expected return on plan assets	0	0
Amortization of prior service cost	0	0
Recognized net actuarial loss	1	0
Total net periodic benefit cost	$ 1	$ 2