Consolidated Company-Sponsored Investment Funds - Summary of Balance Sheet Amounts (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 653,324	$ 998,448	$ 994,510	$ 577,300
Other assets	297,940	193,505
Total assets	8,789,098	9,282,734
Liabilities	4,724,080	4,617,843
Redeemable non-controlling interest	148,809	601,587
Partners' capital attributable to AB Unitholders	3,915,260	4,061,740
Non-redeemable non-controlling interests in consolidated entities	949	1,564
Total liabilities and capital	8,789,098	9,282,734
Company-Sponsored Investment Funds
Variable Interest Entity [Line Items]
Redeemable non-controlling interest	145,921	596,223
Non-redeemable non-controlling interests in consolidated entities	0	757
Reportable Legal Entities | Company-Sponsored Investment Funds
Variable Interest Entity [Line Items]
Cash and cash equivalents	13,118	326,518
Investments	351,696	1,246,283
Other assets	22,840	35,397
Total assets	387,654	1,608,198
Liabilities	22,610	698,101
Redeemable non-controlling interest	145,921	596,223
Partners' capital attributable to AB Unitholders	219,123	313,117
Non-redeemable non-controlling interests in consolidated entities	0	757
Total liabilities and capital	387,654	1,608,198
Reportable Legal Entities | VIEs
Variable Interest Entity [Line Items]
Cash and cash equivalents	11,880	326,158
Investments	217,840	1,189,835
Other assets	6,024	33,931
Total assets	235,744	1,549,924
Liabilities	5,215	695,997
Redeemable non-controlling interest	117,523	596,241
Partners' capital attributable to AB Unitholders	113,006	256,929
Non-redeemable non-controlling interests in consolidated entities	0	757
Total liabilities and capital	235,744	1,549,924
Reportable Legal Entities | VOEs
Variable Interest Entity [Line Items]
Cash and cash equivalents	1,238	360
Investments	133,856	56,448
Other assets	16,816	1,466
Total assets	151,910	58,274
Liabilities	17,395	2,104
Redeemable non-controlling interest	28,398	(18)
Partners' capital attributable to AB Unitholders	106,117	56,188
Non-redeemable non-controlling interests in consolidated entities	0	0
Total liabilities and capital	$ 151,910	$ 58,274