Stock Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation
Stock-based compensation expense recognized	$ 19	$ 20	$ 18
Tax benefit	(7)	(7)	0
After-tax stock-based compensation expense	12	13	18
Cash payments to settle SARs	2	2	1
Cash received from stock option exercises	$ 53	$ 39	$ 22
Restricted Stock Units
Summary of Activity Related to Share-based Compensation
Unvested units, beginning of period	482,177
Units granted	330,388
Units vested	(87,972)
Units forfeited	(51,500)
Unvested units, end of period	673,093.000000	482,177
Weighted Average Grant Date Fair Value Related to Share-based Compensation
Weighted average grant date fair value, unvested units, beginning of period (in dollars per share)	$ 22.36
Weighted average grant date fair value, units granted (in dollars per share)	28.43
Weighted average grant date fair value, units vested (in dollars per share)	13.60
Weighted average grant date fair value, units forfeited (in dollars per share)	26.33
Weighted average grant date fair value, unvested units, end of period (in dollars per share)	$ 26.16	$ 22.36
Performance Share Units
Summary of Activity Related to Share-based Compensation
Unvested units, beginning of period	322,098
Units granted	225,392
Units vested	(157,989)
Units forfeited	(71,231)
Unvested units, end of period	318,270.00000	322,098
Weighted Average Grant Date Fair Value Related to Share-based Compensation
Weighted average grant date fair value, unvested units, beginning of period (in dollars per share)	$ 20.47
Weighted average grant date fair value, units granted (in dollars per share)	28.44
Weighted average grant date fair value, units vested (in dollars per share)	12.29
Weighted average grant date fair value, units forfeited (in dollars per share)	23.93
Weighted average grant date fair value, unvested units, end of period (in dollars per share)	$ 28.64	$ 20.47