Postretirement Benefit Plans Postretirement Benefit Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure
Net loss	$ 20	$ (23)	$ 110
Total recognized in comprehensive income	8	6	(2)
Other Benefits
Defined Benefit Plan Disclosure
Net loss	3	4	12
Defined Benefit Plan, Prior Service Credit	0	(1)	(18)
Amortization of prior service credit	3	3	1
Amortization of net actuarial loss	(3)	(3)	(2)
Foreign Exchange/Other	1	0	0
Change recognized in other comprehensive loss	$ 4	$ 3	$ (7)