Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Shares [Member]	Additional Paid-In Capital [Member]	Treasury Shares [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2012	$ 1,514.1	$ 31.4	$ 722.7	$ (205.5)	$ 776.0	$ 189.5
Net income	143.2	0.0	0.0	0.0	143.2	0.0
Other comprehensive income, net of tax	(41.7)	0.0	0.0	0.0	0.0	(41.7)
Repurchase of common shares (1,098,732, 1,048,144, and 575,115 at a weighted average price of $41.04, $48.48, and $51.58 for 2013, 2014, and 2015 respectively)	(45.1)	0.0	0.0	(45.1)	0.0	0.0
Activity under stock incentive plans	8.7	0.2	8.5	0.0	0.0	0.0
Retirement of common shares (tax payments on equity compensation)	(1.9)	0.0	(1.9)	0.0	0.0	0.0
Deferred tax - share-based payments	0.1	0.0	0.1	0.0	0.0	0.0
Employee stock purchase plan	1.4	0.1	1.3	0.0	0.0	0.0
10% stock dividend	0.0	2.4	96.6	0.0	(99.0)	0.0
Cash dividend declared - common shares	(15.8)	0.0	0.0	0.0	(15.8)	0.0
Ending Balance at Dec. 31, 2013	1,563.0	34.1	827.3	(250.6)	804.4	147.8
Net income	183.2	0.0	0.0	0.0	183.2	0.0
Other comprehensive income, net of tax	(39.7)	0.0	0.0	0.0	0.0	(39.7)
Repurchase of common shares (1,098,732, 1,048,144, and 575,115 at a weighted average price of $41.04, $48.48, and $51.58 for 2013, 2014, and 2015 respectively)	(50.8)	0.0	0.0	(50.8)	0.0	0.0
Activity under stock incentive plans	8.7	0.2	8.5	0.0	0.0	0.0
Retirement of common shares (tax payments on equity compensation)	(1.1)	0.0	(1.1)	0.0	0.0	0.0
Deferred tax - share-based payments	0.1	0.0	0.1	0.0	0.0	0.0
Employee stock purchase plan	1.5	0.0	1.5	0.0	0.0	0.0
Cash dividend declared - common shares	(18.2)	0.0	0.0	0.0	(18.2)	0.0
Ending Balance at Dec. 31, 2014	1,646.7	34.3	836.3	(301.4)	969.4	108.1
Net income	163.2	0.0	0.0	0.0	163.2	0.0
Other comprehensive income, net of tax	(96.6)	0.0	0.0	0.0	0.0	(96.6)
Repurchase of common shares (1,098,732, 1,048,144, and 575,115 at a weighted average price of $41.04, $48.48, and $51.58 for 2013, 2014, and 2015 respectively)	(29.7)	0.0	0.0	(29.7)	0.0	0.0
Activity under stock incentive plans	9.2	0.3	8.9	0.0	0.0	0.0
Retirement of common shares (tax payments on equity compensation)	(4.1)	(0.1)	(4.0)	0.0	0.0	0.0
Deferred tax - share-based payments	0.6	0.0	0.6	0.0	0.0	0.0
Employee stock purchase plan	1.5	0.0	1.5	0.0	0.0	0.0
10% stock dividend	0.0	2.6	121.6	0.0	(124.2)	0.0
Cash dividend declared - common shares	(22.7)	0.0	0.0	0.0	(22.7)	0.0
Ending Balance at Dec. 31, 2015	$ 1,668.1	$ 37.1	$ 964.9	$ (331.1)	$ 985.7	$ 11.5