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	(12.0)	$ (0.1)	(0.7)	(11.2)	0.0
Common stock withheld and retired to cover taxes on vested stock awards (in shares)		(88,000)
Common stock dividends declared	(286.2)	$ 0.0	0.0	(286.2)	0.0
Share-based compensation and other	27.9	$ 0.2	27.6	0.1	0.0
Share-based compensation expense (in shares)		249,000
Comprehensive income	632.3	$ 0.0	0.0	624.6	7.7
Ending Balance at Sep. 30, 2021	3,608.3	$ 1.0	581.3	3,162.8	(136.8)
Ending Balance (in shares) at Sep. 30, 2021		94,991,000
Beginning Balance at Jun. 30, 2021	3,444.3	$ 1.0	574.5	3,008.5	(139.7)
Beginning Balance (in shares) at Jun. 30, 2021		94,979,000
Common stock withheld and retired to cover taxes on vested stock awards	(1.4)	$ 0.0	(0.1)	(1.3)	0.0
Common stock withheld and retired to cover taxes on vested stock awards (in shares)		(10,000)
Common stock dividends declared	(95.3)	$ 0.0	0.0	(95.3)	0.0
Share-based compensation and other	7.1	$ 0.0	6.9	0.2	0.0
Share-based compensation expense (in shares)		22,000
Comprehensive income	253.6	$ 0.0	0.0	250.7	2.9
Ending Balance at Sep. 30, 2021	3,608.3	$ 1.0	581.3	3,162.8	(136.8)
Ending Balance (in shares) at Sep. 30, 2021		94,991,000
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 repurchases and retirements (in shares)		(1,032,000)
Common stock repurchases and retirements	(142.0)	$ 0.0	(8.5)	(133.5)	0.0
Common stock withheld and retired to cover taxes on vested stock awards	(15.3)	$ 0.0	(0.9)	(14.4)	0.0
Common stock withheld and retired to cover taxes on vested stock awards (in shares)		(110,000)
Common stock dividends declared	(328.6)	$ 0.0	0.0	(328.6)	0.0
Share-based compensation and other	30.3	$ 0.0	30.6	(0.3)	0.0
Share-based compensation expense (in shares)		304,000
Comprehensive income	819.6	$ 0.0	0.0	818.2	1.4
Ending Balance at Sep. 30, 2022	3,971.2	$ 0.9	600.6	3,443.5	(73.8)
Ending Balance (in shares) at Sep. 30, 2022		92,701,000
Beginning Balance at Jun. 30, 2022	3,964.5	$ 0.9	601.0	3,437.0	(74.4)
Beginning Balance (in shares) at Jun. 30, 2022		93,686,000
Common stock repurchases and retirements (in shares)		(1,032,000)
Common stock repurchases and retirements	(142.0)	$ 0.0	(8.5)	(133.5)	0.0
Common stock withheld and retired to cover taxes on vested stock awards	(5.9)	$ 0.0	(0.4)	(5.5)	0.0
Common stock withheld and retired to cover taxes on vested stock awards (in shares)		(43,000)
Common stock dividends declared	(116.7)	$ 0.0	0.0	(116.7)	0.0
Share-based compensation and other	8.2	$ 0.0	8.5	(0.3)	0.0
Share-based compensation expense (in shares)		90,000
Comprehensive income	263.1	$ 0.0	0.0	262.5	0.6
Ending Balance at Sep. 30, 2022	$ 3,971.2	$ 0.9	$ 600.6	$ 3,443.5	$ (73.8)
Ending Balance (in shares) at Sep. 30, 2022		92,701,000