Condensed Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Retained Earnings
Balance at Dec. 31, 2020		$ 158.0	$ 2,137.8	$ (689.9)	$ (155.1)
Common stock repurchased and retired		0.0	0.0
Common stock issued for stock options exercised	$ 25.7	1.2	24.5
Common stock issued for other transactions			1.4
Stock-based compensation			0.6
Other comprehensive income	6.2			6.2
Net income	243.6				243.6
Common stock dividends paid					(31.7)
Balance at Mar. 31, 2021	1,696.6	$ 159.2	2,164.3	(683.7)	56.8
Dividends declared per share of common stock		$ 0.20
Balance at Dec. 31, 2021	2,652.2	$ 156.8	1,969.6	(488.0)	1,013.8
Common stock repurchased and retired	(263.2)	(5.2)	(258.0)
Common stock issued for stock options exercised	5.2	0.2	5.0
Common stock issued for other transactions			2.2
Stock-based compensation			0.5
Other comprehensive income	26.8			26.8
Net income	393.0				393.0
Common stock dividends paid					(30.8)
Balance at Mar. 31, 2022	$ 2,785.9	$ 151.8	$ 1,719.3	$ (461.2)	$ 1,376.0
Dividends declared per share of common stock		$ 0.20