Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance at Dec. 31, 2020	$ 3,246.3	$ 0.9	$ 554.4	$ 2,835.5	$ (144.5)
Beginning Balance (in shares) at Dec. 31, 2020		94,830,000
Common stock withheld and retired to cover taxes on vested stock awards	0.1			0.1
Common stock withheld and retired to cover taxes on vested stock awards (in shares)		1,000
Common stock dividends declared	(95.5)			(95.5)
Share-based compensation and other	11.6	$ 0.1	11.6	(0.1)
Share-based compensation expense (in shares)		165,000
Comprehensive income	168.9	$ 0.0	0.0	166.5	2.4
Ending Balance at Mar. 31, 2021	3,331.2	$ 1.0	566.0	2,906.3	(142.1)
Ending Balance (in shares) at Mar. 31, 2021		94,994,000
Beginning Balance at Dec. 31, 2021	3,607.2	$ 0.9	579.4	3,102.1	(75.2)
Beginning Balance (in shares) at Dec. 31, 2021		93,539,000
Common stock withheld and retired to cover taxes on vested stock awards	(0.2)	$ 0.0	0.0	(0.2)	0.0
Common stock withheld and retired to cover taxes on vested stock awards (in shares)		(1,000)
Common stock dividends declared	(94.2)	$ 0.0	0.0	(94.2)	0.0
Share-based compensation and other	12.3	$ 0.0	12.3	0.0	0.0
Share-based compensation expense (in shares)		166,000
Comprehensive income	254.2	$ 0.0	0.0	254.2	0.0
Ending Balance at Mar. 31, 2022	$ 3,779.3	$ 0.9	$ 591.7	$ 3,261.9	$ (75.2)
Ending Balance (in shares) at Mar. 31, 2022		93,704,000