Employee Pension and Other Postretirement Benefits (Details 2) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 24	$ 21	$ 72	$ 60
Interest cost	27	25	82	79
Expected return on plan assets	(54)	(49)	(162)	(144)
Amortization of prior service cost	(4)	(4)	(13)	(7)
Recognized net actuarial loss	27	16	80	43
Total net periodic benefit cost	20	9	59	31
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	4	2	8	8
Interest cost	4	3	9	9
Expected return on plan assets	(6)	(5)	(15)	(14)
Amortization of prior service cost	(2)	(2)	(6)	(3)
Recognized net actuarial loss	7	0	9	1
Total net periodic benefit cost	7	(2)	5	1
Superannuation, SERP and ESBP
Components of net periodic benefit cost:
Service cost	0	0	1	1
Interest cost	0	1	1	3
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Recognized net actuarial loss	1	0	2	1
Total net periodic benefit cost	$ 1	$ 1	$ 4	$ 5