Share-Based Compensation (PSU Compensation Expense) (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		$ 9.41
PSU expense before income tax		$ 6	$ 5	$ 6
Tax benefit		(2)	(1)	(2)
compensation expense, net of tax		4	4	4
Total value of PSUs converted	[1]	1	1	4
Total fair value of PSUs vested		$ 3	$ 3	$ 1
Performance Stock Units With Market Conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		$ 9.41	$ 8.22	$ 15.19

[1] Amount represents fair market value on the date of conversion.