Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Revenues
Total revenues	$ 1,883.2	$ 1,693.7	$ 1,375.2
Cost of revenues
Operating expenses	267.4	223.7	169.8
Depreciation and amortization	67.2	52.6	42.9
Total cost of revenues	334.6	276.3	212.7
Administrative expenses
Sales and marketing	434.4	417.6	346.6
Research and development	242.6	199.0	148.3
General and administrative	158.6	288.1	239.1
Depreciation and amortization	78.7	61.4	49.8
Total administrative expenses	914.3	966.1	783.8
Total operating expenses	1,248.9	1,242.4	996.5
Operating income	634.3	451.3	378.7
Interest expense	(3.4)	(1.9)	(2.5)
Other income (expense), net	18.1	23.0	13.4
Income before income taxes	649.0	472.4	389.6
Provision for income taxes	147.0	131.6	108.2
Net income	$ 502.0	$ 340.8	$ 281.4
Earnings per share, basic	$ 8.93	$ 5.91	$ 4.86
Earnings per share, diluted	$ 8.92	$ 5.88	$ 4.84
Weighted average shares outstanding:
Basic	56,208	57,707	57,928
Diluted	56,296	57,974	58,175
Comprehensive earnings:
Net income	$ 502.0	$ 340.8	$ 281.4
Unrealized net gains (losses) on available-for-sale securities	1.0	3.5	(4.8)
Tax effect	(0.6)	(0.8)	1.1
Other comprehensive income (loss), net of tax	0.4	2.7	(3.7)
Comprehensive earnings:	502.4	343.5	277.7
Recurring and Other [Member]
Revenues
Total revenues	1,758.3	1,585.7	1,342.5
Interest on Funds Held for Clients [Member]
Revenues
Total revenues	$ 124.9	$ 108.0	$ 32.7