Common Shares And Stock-Based Awards Plans (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions		1 Months Ended	12 Months Ended
	Jan. 13, 2020	Feb. 29, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 19, 2020	Oct. 26, 2018	Mar. 06, 2018	Dec. 07, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares available for issuance			3,300
Number of options, exercisable			270	300	400
Weighted-average exercise price of options exercisable			$ 20.02	$ 20.07	$ 18.56
Equity [Abstract]
Quarterly cash dividend declared			$ 0.15
Dividend declared date			Dec. 16, 2019
Dividend record date			Dec. 30, 2019
Dividends paid			$ 23.3	$ 21.0
Dividend paid date			Jan. 13, 2020
Common Shares Note [Abstract]
Repurchase of common shares program authorized amount							$ 100.0	$ 250.0	$ 100.0
Repurchase of common shares remaining authorized amount			$ 79.5
Repurchase of common Shares			4,700	8,200	1,000
Repurchase of common shares, value			$ 122.1	$ 211.9	$ 29.3
Repurchase of common shares, average cost per share			$ 25.86	$ 25.71	$ 30.46
Subsequent Event [Member]
Equity [Abstract]
Quarterly cash dividend declared		$ 0.16
Dividends paid	$ 5.5
Common Shares Note [Abstract]
Repurchase of common shares program authorized amount						$ 150.0
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of options			10 years
Employee Awards [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Employee Awards [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Employee Awards [Member] | Performance-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Non-Employee Awards [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			1 year