Earnings Per Share - Schedule of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Numerator:
Net income	$ 67,968	$ 111,111	$ 75,612	$ 65,704
Net income attributable to noncontrolling interest	76,949		85,107
Net loss attributable to Andersen Group Inc. stockholders, basic	(8,981)		(9,495)
Net loss attributable to Andersen Group Inc. stockholders, diluted	$ (8,981)		$ (9,495)
Denominator:
Weighted average number of shares of Class A common stock outstanding, basic (in shares)	16,215,709		14,055,314
Weighted-average shares of Class A common stock outstanding, diluted (in shares)	16,215,709		14,055,314
Earnings per share:
Earnings per share attributable to Class A common stockholders, basic (in dollars per share)	$ (0.55)		$ (0.68)
Earnings per share attributable to Class A common stockholders, diluted (in dollars per share)	$ (0.55)		$ (0.68)