Consolidated Company-Sponsored Investment Funds - Summary of Balance Sheet Amounts (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Other assets	$ 330,943	$ 297,940
Total assets	8,706,092	8,789,098
Liabilities	4,363,430	4,724,080
Redeemable non-controlling interest	325,561	148,809
Partners' capital attributable to AB Unitholders	4,017,101	3,915,260
Total liabilities, redeemable non-controlling interest and capital	8,706,092	8,789,098
Consolidated company-sponsored investment funds
Variable Interest Entity [Line Items]
Redeemable non-controlling interest	325,561	145,921
Reportable Legal Entities | Consolidated company-sponsored investment funds
Variable Interest Entity [Line Items]
Cash and cash equivalents	11,433	13,118
Investments	581,004	351,696
Other assets	19,810	22,840
Total assets	612,247	387,654
Liabilities	31,017	22,610
Redeemable non-controlling interest	325,561	145,921
Partners' capital attributable to AB Unitholders	255,669	219,123
Total liabilities, redeemable non-controlling interest and capital	612,247	387,654
Reportable Legal Entities | VIEs
Variable Interest Entity [Line Items]
Cash and cash equivalents	9,623	11,880
Investments	404,624	217,840
Other assets	9,618	6,024
Total assets	423,865	235,744
Liabilities	12,147	5,215
Redeemable non-controlling interest	273,219	117,523
Partners' capital attributable to AB Unitholders	138,499	113,006
Total liabilities, redeemable non-controlling interest and capital	423,865	235,744
Reportable Legal Entities | VOEs
Variable Interest Entity [Line Items]
Cash and cash equivalents	1,810	1,238
Investments	176,380	133,856
Other assets	10,192	16,816
Total assets	188,382	151,910
Liabilities	18,870	17,395
Redeemable non-controlling interest	52,342	28,398
Partners' capital attributable to AB Unitholders	117,170	106,117
Total liabilities, redeemable non-controlling interest and capital	$ 188,382	$ 151,910