Condensed Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income Statement [Abstract]
Revenue	$ 617.4	$ 569.4	$ 1,804.4	$ 1,684.1
Operating expense:
Cost of revenue	241.7	222.7	703.7	663.5
Sales and marketing	115.5	107.9	347.8	323.8
General and administrative	85.9	77.6	244.4	238.2
Depreciation and amortization	47.0	45.7	142.8	142.0
Total operating expense	490.1	453.9	1,438.7	1,367.5
Other operating income	0.5	0.0	1.3	0.0
Operating income	127.8	115.5	367.0	316.6
Non-operating income (expense), net:
Interest expense, net	(7.0)	(8.9)	(19.8)	(30.7)
Gain on sale of business	0.0	45.3	0.0	45.3
Other income (expense), net	2.3	0.0	0.9	(2.8)
Non-operating income (expense), net	(4.7)	36.4	(18.9)	11.8
Income before income taxes and equity in investments of unconsolidated entities	123.1	151.9	348.1	328.4
Equity in investments of unconsolidated entities	(0.1)	(2.6)	(3.9)	(5.3)
Income tax expense	31.4	29.6	85.1	70.1
Consolidated net income	$ 91.6	$ 119.7	$ 259.1	$ 253.0
Net income per share:
Basic (in dollars per share)	$ 2.18	$ 2.79	$ 6.12	$ 5.91
Diluted (in dollars per share)	2.17	2.77	6.08	5.87
Dividends declared (in dollars per share)	0.46	0.41	1.37	1.22
Dividends paid per common share (in dollars per share)	$ 0.46	$ 0.41	$ 1.37	$ 1.22
Weighted average shares outstanding:
Basic (in shares)	42.1	42.9	42.4	42.8
Diluted (in shares)	42.3	43.2	42.6	43.1