Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	$ 1,075,985	$ 1,029,202	$ 2,159,856	$ 2,101,002
Not subject to contracts with customers:
Dividend and interest income, net of broker-dealer related interest expense	20,475	22,173	37,308	42,971
Investment (losses)	(7,825)	(23,629)	(28,363)	(11,886)
Other revenues	272	197	713	7
Total revenue not from contract with customer	12,922	(1,259)	9,658	31,092
Net revenues	1,088,907	1,027,943	2,169,514	2,132,094
Base fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	805,319	774,017	1,623,185	1,528,256
Performance-based fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	38,659	43,310	75,905	73,476
Bernstein research services
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	0	0	0	96,222
All-in-management fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	86,926	81,680	175,370	160,104
12b-1 fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	15,248	16,569	31,500	33,174
Other distribution fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	96,193	74,656	190,517	145,317
Shareholder servicing fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	21,278	22,356	37,920	44,019
JV related revenues
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	9,013	12,977	18,347	12,977
Other
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	$ 3,349	$ 3,637	$ 7,112	$ 7,457