Pension Plans, Retirement Benefits and Savings Plans (details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Pension Plans [Member]
Defined benefit plan disclosure
Service cost	$ 29	$ 33	$ 88	$ 98
Interest cost on benefit obligation	30	36	91	108
Expected return on plan assets	(57)	(58)	(172)	(173)
Net periodic benefit cost, settlement			1
Net periodic benefit cost, amortization of unrecognized net actuarial loss	17	24	50	72
Net periodic benefit cost	19	35	58	105
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Interest cost on benefit obligation	2	3	6	8
Net periodic benefit cost, amortization of unrecognized prior service benefit	(1)	(1)	(3)	(2)
Net periodic benefit cost	$ 1	$ 2	$ 3	$ 6