Employee Pension and Other Postretirement Benefits (Details 2) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 23	$ 18	$ 48	$ 39
Interest cost	28	26	55	54
Expected return on plan assets	(54)	(47)	(108)	(95)
Amortization of prior service cost	(5)	(3)	(9)	(3)
Recognized net actuarial loss	26	14	53	28
Total net periodic benefit cost	18	8	39	23
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	2	2	4	5
Interest cost	2	3	5	6
Expected return on plan assets	(4)	(4)	(9)	(9)
Amortization of prior service cost	(2)	(1)	(4)	(1)
Recognized net actuarial loss	1	0	2	0
Total net periodic benefit cost	(1)	0	(2)	1
Superannuation, SERP and ESBP
Components of net periodic benefit cost:
Service cost	1	0	1	1
Interest cost	1	1	1	2
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Recognized net actuarial loss	0	1	1	1
Total net periodic benefit cost	$ 2	$ 2	$ 3	$ 4