Share-Based Compensation Plans Share-Based Compensation Plans (Summary of ROIC Performance Share Unit Grants) (Details) - Return on Invested Capital Performance-Based Shares [Member] - Performance Based Shares shares in Thousands	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Summary of performance share activity
Outstanding, beginning of period (in shares) | shares	298
Granted (in shares) | shares	76
Forfeited (in shares) | shares	(93)
Outstanding, end of period (in shares) | shares	281
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding, beginning of period (in usd per share) | $ / shares	$ 41.48
Granted (in usd per share) | $ / shares	75.18
Forfeited (in usd per share) | $ / shares	36.69
Outstanding, end of period (in usd per share) | $ / shares	$ 52.14