Earnings per Share - Schedule of Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Numerator
Net income attributable to ACIC common stockholders	$ 19,254	$ 21,348
Denominator
Weighted-average shares outstanding	48,546,290	48,135,231
Effect of dilutive securities	1,262,542	1,429,490
Weighted-average diluted shares	49,808,832	49,564,721
Earnings available to ACIC common stockholders per share, Basic	$ 0.4	$ 0.44
Earnings available to ACIC common stockholders per share, Diluted	$ 0.39	$ 0.43