Consolidated Company-Sponsored Investment Funds - Summary of Balance Sheet Amounts (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024
Condensed Balance Sheet Statements, Captions [Line Items]
Total assets	$ 9,064,066	$ 9,071,927
Liabilities	4,163,531	4,148,795
Redeemable non-controlling interest	159,673	48,489
Partners' capital attributable to AB Unitholders	4,740,862	4,874,643	$ 4,588,134
Total liabilities, redeemable non-controlling interest and partners' capital	9,064,066	9,071,927
Company-Sponsored Investment Funds
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	12,065	1,989
Investments	353,643	140,792
Other assets	29,943	14,801
Total assets	395,651	157,582
Liabilities	34,045	1,716
Redeemable non-controlling interest	159,673	48,489
Partners' capital attributable to AB Unitholders	201,933	107,377
Total liabilities, redeemable non-controlling interest and partners' capital	395,651	157,582
VIEs
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	12,027	1,671
Investments	320,922	82,027
Other assets	29,235	1,317
Total assets	362,184	85,015
Liabilities	33,488	345
Redeemable non-controlling interest	152,494	31,670
Partners' capital attributable to AB Unitholders	176,202	53,000
Total liabilities, redeemable non-controlling interest and partners' capital	362,184	85,015
VOEs
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	38	318
Investments	32,721	58,765
Other assets	708	13,484
Total assets	33,467	72,567
Liabilities	557	1,371
Redeemable non-controlling interest	7,179	16,819
Partners' capital attributable to AB Unitholders	25,731	54,377
Total liabilities, redeemable non-controlling interest and partners' capital	$ 33,467	$ 72,567