Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 14	$ 9	$ 41	$ 29
Interest cost on projected benefit obligation	22	19	66	59
Expected return on plan assets	(32)	(23)	(96)	(70)
Amortization of unrecognized loss	9	5	22	14
Net periodic benefit cost	13	10	33	32
Postretirement Benefits Other Than Pensions (OPEB) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	5	3	14	8
Interest cost on projected benefit obligation	7	5	22	15
Amortization of prior service cost/(credit)	(1)	(1)	(3)	(3)
Amortization of unrecognized loss	1	1	6	2
Net periodic benefit cost	$ 12	$ 8	$ 39	$ 22