Consolidated Company-Sponsored Investment Funds - Summary of Balance Sheet Amounts (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 998,448	$ 994,510	$ 541,483	$ 555,503
Other assets	211,893	195,615
Total assets	9,295,167	8,741,158
Liabilities	4,630,276	4,280,010
Redeemable non-controlling interest	601,587	392,959
Partners' capital attributable to AB Unitholders	4,061,740	4,032,017
Non-redeemable non-controlling interests in consolidated entities	1,564	36,172
Total liabilities and capital	9,295,167	8,741,158
Company-Sponsored Investment Funds [Member]
Variable Interest Entity [Line Items]
Redeemable non-controlling interest	596,223	384,294
Non-redeemable non-controlling interests in consolidated entities	757	34,622
Reportable Legal Entities [Member] | Company-Sponsored Investment Funds [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents	326,518	337,525
Investments	1,246,283	570,876
Other assets	35,397	48,480
Total assets	1,608,198	956,881
Liabilities	698,101	293,510
Redeemable non-controlling interest	596,223	384,294
Partners' capital attributable to AB Unitholders	313,117	244,455
Non-redeemable non-controlling interests in consolidated entities	757	34,622
Total liabilities and capital	1,608,198	956,881
Reportable Legal Entities [Member] | VIEs [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents	326,158	337,525
Investments	1,189,835	547,650
Other assets	33,931	48,480
Total assets	1,549,924	933,655
Liabilities	695,997	293,510
Redeemable non-controlling interest	596,241	384,294
Partners' capital attributable to AB Unitholders	256,929	221,229
Non-redeemable non-controlling interests in consolidated entities	757	34,622
Total liabilities and capital	1,549,924	933,655
Reportable Legal Entities [Member] | VOEs [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents	360	0
Investments	56,448	23,226
Other assets	1,466	0
Total assets	58,274	23,226
Liabilities	2,104	0
Redeemable non-controlling interest	(18)	0
Partners' capital attributable to AB Unitholders	56,188	23,226
Non-redeemable non-controlling interests in consolidated entities	0	0
Total liabilities and capital	$ 58,274	$ 23,226