Employment Benefit Plans Net Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 46	$ 48	$ 38
Interest cost	95	90	95
Expected return on plan assets	(142)	(138)	(134)
Amortization of prior service credits	(1)	(1)	(1)
Amortization of net loss	1	2	1
Settlements	(1)	(1)	(1)
Net (benefit) cost recognized	(2)	0	(2)
Retiree Health and Welfare Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	1	1	1
Interest cost	10	10	11
Amortization of prior service credits	(2)	(2)	(2)
Amortization of net loss	1	2	1
Net (benefit) cost recognized	$ 10	$ 11	$ 11