Earnings per Share - Schedule of Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Numerator
Net income attributable to ACIC common stockholders	$ 106,837	$ 75,718	$ 309,911
Denominator
Weighted-average shares outstanding	48,476,824	47,831,412	43,596,432
Effect of dilutive securities	1,306,169	1,531,573	792,372
Weighted-average diluted shares	49,782,993	49,362,985	44,388,804
Earnings available to ACIC common stockholders per share, Basic	$ 2.2	$ 1.59	$ 7.11
Earnings available to ACIC common stockholders per share, Diluted	$ 2.15	$ 1.54	$ 6.98