Pension Plans, Retirement Benefits and Savings Plans (details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Plans [Member]
Defined benefit plan disclosure
Service cost	$ 29	$ 33
Interest cost on benefit obligation	30	36
Expected return on plan assets	(57)	(58)
Net periodic benefit cost, amortization of unrecognized net actuarial loss	17	24
Net periodic benefit cost	19	35
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Interest cost on benefit obligation	2	3
Net periodic benefit cost, amortization of unrecognized prior service benefit	(1)	(1)
Net periodic benefit cost	$ 1	$ 2