Capital Stock - Shares Used To Calculate Earnings (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Equity [Abstract]
Basic (shares)	50.2	51.2	50.1	51.0
Effect of dilutive stock options and awards (shares)	0.7	0.0	0.8	0.0
Diluted (shares)	50.9	51.2	50.9	51.0
Antidilutive stock options and awards excluded from denominator (shares)	0.1	1.6	0.1	1.7
Deferred compensation common stock unit (shares)	0.3	0.3	0.3	0.3