Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	$ 1,057,699	$ 1,016,275	$ 3,145,724	$ 2,995,208
Not subject to contracts with customers:
Dividend and interest income, net of broker-dealer related interest expense	17,726	22,391	60,697	69,793
Investment (losses)	(3,512)	(6,694)	(15,398)	(760)
Other revenues	13,576	84	26,560	362
Total revenue not from contract with customer	27,790	15,781	71,859	69,395
Net revenues	1,085,489	1,032,056	3,217,583	3,064,603
Base fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	813,623	720,969	2,341,879	2,116,668
Performance-based fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	28,763	27,982	102,239	82,868
Bernstein research services(1)
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	0	93,875	96,222	285,760
All-in-management fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	87,396	72,240	247,500	211,877
12b-1 fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	17,128	16,388	50,302	47,321
Other distribution fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	84,692	60,421	230,009	175,727
Shareholder servicing fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	22,624	21,539	66,643	62,633
Other
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	$ 3,473	$ 2,861	$ 10,930	$ 12,354