Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	$ 1,016,225	$ 982,926	$ 2,088,025	$ 1,978,933
Not subject to contracts with customers:
Dividend and interest income, net of broker-dealer related interest expense	22,173	24,744	42,971	47,402
Investment (losses) gains	(23,629)	670	(11,886)	5,934
Other revenues	13,174	116	12,984	278
Total revenue not from contract with customer	11,718	25,530	44,069	53,614
Net revenues	1,027,943	1,008,456	2,132,094	2,032,547
Base fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	774,017	703,371	1,528,256	1,395,699
Performance-based fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	43,310	18,307	73,476	54,886
Bernstein research services(1)
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	0	91,847	96,222	191,885
All-in-management fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	81,680	70,849	160,104	139,637
12b-1 fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	16,569	15,778	33,174	30,933
Other distribution fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	74,656	58,171	145,317	115,306
Shareholder servicing fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	22,356	20,801	44,019	41,094
Other
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	$ 3,637	$ 3,802	$ 7,457	$ 9,493