Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	$ 1,118,224	$ 1,071,221	$ 3,278,080	$ 3,172,223
Not subject to contracts with customers:
Dividend and interest income, net of broker-dealer related interest expense	20,741	17,726	58,049	60,697
Investment (losses)	(2,721)	(3,512)	(31,084)	(15,398)
Other revenues	903	54	1,616	61
Total revenue not from contract with customer	18,923	14,268	28,581	45,360
Net revenues	1,137,147	1,085,489	3,306,661	3,217,583
Base fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	852,478	813,623	2,475,663	2,341,879
Performance-based fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	21,972	28,763	97,877	102,239
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	90,754	87,396	266,124	247,500
12b-1 fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	16,008	17,128	47,508	50,302
Other distribution fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	103,662	84,692	294,179	230,009
Shareholder servicing fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	21,176	22,624	59,096	66,643
JV related revenues
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	9,242	13,522	27,589	26,499
Other
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	$ 2,932	$ 3,473	$ 10,044	$ 10,930