Consolidated Company-Sponsored Investment Funds - Summary of Balance Sheet Amounts (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Other assets	$ 264,418	$ 330,943
Total assets	9,697,840	8,706,092
Liabilities	5,483,958	4,363,430
Redeemable non-controlling interest	102,359	325,561
Partners' capital attributable to AB Unitholders	4,111,523	4,017,101
Total liabilities, redeemable non-controlling interest and capital	9,697,840	8,706,092
Consolidated company-sponsored investment funds
Variable Interest Entity [Line Items]
Cash and cash equivalents	36,506	11,433
Investments	302,582	581,004
Other assets	12,244	19,810
Redeemable non-controlling interest	102,359	325,561
Reportable Legal Entities | Consolidated company-sponsored investment funds
Variable Interest Entity [Line Items]
Cash and cash equivalents	36,506	11,433
Investments	302,582	581,004
Other assets	12,244	19,810
Total assets	351,332	612,247
Liabilities	30,620	31,017
Redeemable non-controlling interest	102,359	325,561
Partners' capital attributable to AB Unitholders	218,353	255,669
Total liabilities, redeemable non-controlling interest and capital	351,332	612,247
Reportable Legal Entities | VIEs
Variable Interest Entity [Line Items]
Cash and cash equivalents	36,370	9,623
Investments	242,541	404,624
Other assets	4,859	9,618
Total assets	283,770	423,865
Liabilities	7,741	12,147
Redeemable non-controlling interest	82,753	273,219
Partners' capital attributable to AB Unitholders	193,276	138,499
Total liabilities, redeemable non-controlling interest and capital	283,770	423,865
Reportable Legal Entities | VOEs
Variable Interest Entity [Line Items]
Cash and cash equivalents	136	1,810
Investments	60,041	176,380
Other assets	7,385	10,192
Total assets	67,562	188,382
Liabilities	22,879	18,870
Redeemable non-controlling interest	19,606	52,342
Partners' capital attributable to AB Unitholders	25,077	117,170
Total liabilities, redeemable non-controlling interest and capital	$ 67,562	$ 188,382