Earnings per Share - Computation of Basic and Diluted EPS (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Net income attributable to SS&C common stockholders	$ 156.0	$ 160.0	$ 412.7	$ 442.7
Shares attributable to SS&C:
Weighted-average common shares outstanding – used in calculation of basic EPS	247,500,000	253,900,000	248,800,000	254,800,000
Weighted-average common stock equivalents – stock options and restricted shares	6,400,000	7,000,000	6,500,000	8,900,000
Weighted-average common and common equivalent shares outstanding – used in calculation of diluted EPS	253,900,000	260,900,000	255,300,000	263,700,000
Earnings per share attributable to SS&C common stockholders - Basic	$ 0.63	$ 0.63	$ 1.66	$ 1.74
Earnings per share attributable to SS&C common stockholders - Diluted	$ 0.61	$ 0.61	$ 1.62	$ 1.68