Segment Reporting - Schedule of Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Revenue	$ 240,746	$ 208,067
Operating expenses:
Total operating income	24,080	52,647
Interest income	1,879	1,200
Interest expense	(6,234)	(143)
Other income, net	826	1,002
Income before income tax expense	20,551	54,706
Income tax expense	2,813	4,130
Net income attributable to Andersen Group Inc.	494
Reportable Segment
Segment Reporting Information [Line Items]
Revenue	240,746	208,067
Operating expenses:
Personnel costs	175,685	115,911
Non-personnel and other operating costs	38,707	37,414
Depreciation and amortization	2,274	2,095
Total operating expenses	216,666	155,420
Total operating income	24,080	52,647
Interest income	1,879	1,200
Interest expense	(6,234)	(143)
Other income, net	826	1,002
Income before income tax expense	20,551	54,706
Income tax expense	2,813	4,130
Net income attributable to Andersen Group Inc.	$ 17,738	$ 50,576