Earnings per Share - Computation of Basic and Diluted EPS (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Earnings Per Share [Abstract]
Net income attributable to SS&C common stockholders	$ 126.0	$ 172.1
Shares attributable to SS&C:
Weighted-average common shares outstanding – used in calculation of basic EPS	250,400,000	255,800,000
Weighted-average common stock equivalents – stock options and restricted shares	6,600,000	11,800,000
Weighted-average common and common equivalent shares outstanding – used in calculation of diluted EPS	257,000,000.0	267,600,000
Earnings per share attributable to SS&C common stockholders - Basic	$ 0.50	$ 0.67
Earnings per share attributable to SS&C common stockholders - Diluted	$ 0.49	$ 0.64