Common Shares And Stock-Based Awards Plans (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions		3 Months Ended	12 Months Ended
	Jan. 11, 2019	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	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		2,700	2,700
Number of options, exercisable		340	340	400	900
Weighted-average exercise price of options exercisable		$ 20.07	$ 20.07	$ 18.56	$ 18.53
Equity [Abstract]
Quarterly cash dividend declared		$ 0.15
Dividend declared date		Dec. 17, 2018
Dividend record date		Dec. 31, 2018
Dividends paid			$ 21.0
Dividend paid date		Jan. 11, 2019
Common Shares Note [Abstract]
Repurchase of common shares program authorized amount						$ 100.0	$ 250.0	$ 100.0
Repurchase of common shares remaining authorized amount		$ 201.6	$ 201.6
Repurchase of common Shares			8,200	1,000	2,000
Repurchase of common shares, value			$ 211.9	$ 29.3	$ 41.9
Repurchase of common shares, average cost per share			$ 25.71	$ 30.46	$ 21.4
Subsequent Event [Member]
Equity [Abstract]
Dividends paid	$ 6.2
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