Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Cumulative Effect, Period of Adoption, Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period, Shares				(30,700,000)
Dividends Declared [Table Text Block]	1.84
Balance at beginning of year at Dec. 31, 2018			67,300,000
Balance at beginning of period, Common Stock at Dec. 31, 2018			$ 41.6
Balance at beginning of period at Dec. 31, 2018				$ (1,214.5)	$ 706.4	$ 2,419.2		$ (164.6)	$ (164.6)
Balance at beginning of period (Retained Earnings [Member]) at Dec. 31, 2018		$ 39.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, Shares			200,000
Issuance of common stock			$ 0.2
Stock repurchases, Shares	2,000,000.0
Stock repurchases	$ (150.0)
Share-based compensation effects					13.7
Net income	211.2
Dividends declared ($2.00 in 2021, $1.92 in 2020 and $1.84 in 2019)						68.5
Other comprehensive income (loss)	1.0	1.0
Balance at end of period, Common Stock, Shares at Dec. 31, 2019			67,500,000
Balance at end of period, Common Stock at Dec. 31, 2019			$ 41.8
Balance at end of period at Dec. 31, 2019	$ 1,835.1			$ (1,364.5)	720.1	2,601.3	$ 2,601.3	(163.6)	(163.6)
Balance at end of period (Retained Earnings [Member]) at Dec. 31, 2019		0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period, Shares				(32,700,000)
Dividends Declared [Table Text Block]	1.92
Issuance of common stock, Shares			300,000
Issuance of common stock			$ 0.1
Stock repurchases, Shares	0
Stock repurchases	$ 0.0
Share-based compensation effects					15.3
Net income	151.3
Dividends declared ($2.00 in 2021, $1.92 in 2020 and $1.84 in 2019)						70.5
Other comprehensive income (loss)	$ 26.1	26.1
Balance at end of period, Common Stock, Shares at Dec. 31, 2020	67,751,074		67,800,000
Balance at end of period, Common Stock at Dec. 31, 2020	$ 41.9		$ 41.9
Balance at end of period at Dec. 31, 2020	$ 1,957.4			$ (1,364.5)	735.4	2,682.1	2,682.1	(137.5)	(137.5)
Balance at end of period (Retained Earnings [Member]) at Dec. 31, 2020		0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period, Shares				(32,700,000)
Dividends Declared [Table Text Block]	2.00
Issuance of common stock, Shares			500,000
Issuance of common stock			$ 0.3
Stock repurchases, Shares	100,000
Stock repurchases	$ (13.1)
Share-based compensation effects					28.4
Net income	$ 143.1
Dividends declared ($2.00 in 2021, $1.92 in 2020 and $1.84 in 2019)						$ 73.7
Other comprehensive income (loss)		$ (23.1)
Balance at end of period, Common Stock, Shares at Dec. 31, 2021	68,254,574		68,300,000
Balance at end of period, Common Stock at Dec. 31, 2021	$ 42.2		$ 42.2
Balance at end of period at Dec. 31, 2021	2,019.2			$ (1,377.7)	$ 763.8		$ 2,751.5	$ (160.6)	$ (160.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Repurchased During Period, Value	$ 13.2
Balance at beginning of period, Shares				(32,800,000)