Consolidated Company-Sponsored Investment Funds (Summary of Balance Sheet Amounts) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,247,459	$ 994,510	$ 838,162	$ 577,300
Other assets	231,249	195,615
Total assets	9,184,651	8,740,448
Liabilities	4,866,645	4,279,300
Redeemable non-controlling interest	421,618	392,959
Partners' capital attributable to AB Unitholders	3,894,781	4,032,017
Non-redeemable non-controlling interests in consolidated entities	1,607	36,172
Total liabilities, redeemable non-controlling interest and capital	9,184,651	8,740,448
Company-sponsored investment funds
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	445,250	337,525
Investments	799,935	574,076
Other assets	6,455	44,570
Liabilities	593,800	292,800
Redeemable non-controlling interest	416,254	384,294
Non-redeemable non-controlling interests in consolidated entities	841	34,622
Reportable entities | Company-sponsored investment funds
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	445,250	337,525
Investments	799,935	574,076
Other assets	6,455	44,570
Total assets	1,251,640	956,171
Liabilities	593,800	292,800
Redeemable non-controlling interest	416,254	384,294
Partners' capital attributable to AB Unitholders	240,745	244,455
Non-redeemable non-controlling interests in consolidated entities	841	34,622
Total liabilities, redeemable non-controlling interest and capital	1,251,640	956,171
Reportable entities | VIEs
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	445,176	337,525
Investments	770,953	550,850
Other assets	5,850	44,570
Total assets	1,221,979	932,945
Liabilities	591,231	292,800
Redeemable non-controlling interest	415,761	384,294
Partners' capital attributable to AB Unitholders	214,146	221,229
Non-redeemable non-controlling interests in consolidated entities	841	34,622
Total liabilities, redeemable non-controlling interest and capital	1,221,979	932,945
Reportable entities | VOEs
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	74	0
Investments	28,982	23,226
Other assets	605	0
Total assets	29,661	23,226
Liabilities	2,569	0
Redeemable non-controlling interest	493	0
Partners' capital attributable to AB Unitholders	26,599	23,226
Non-redeemable non-controlling interests in consolidated entities	0	0
Total liabilities, redeemable non-controlling interest and capital	$ 29,661	$ 23,226