Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	$ 841,442	$ 781,519	$ 2,497,449	$ 2,274,467
Dividend and interest income, net of interest expense	7,467	10,906	35,204	33,825
Investment gains (losses)	565	18,808	26,860	68,122
Other revenues	702	917	3,188	2,966
Revenue not subject to contract with customer	8,734	30,631	65,252	104,913
Net revenues	850,176	812,150	2,562,701	2,379,380
Base fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	568,918	538,552	1,699,584	1,547,213
Performance-based fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	41,145	4,555	82,703	25,347
Bernstein research services
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	103,581	108,385	324,192	330,596
All-in-management fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	62,807	64,495	193,884	177,637
12b-1 fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	22,136	23,199	66,746	71,677
Other
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	19,545	18,348	56,980	53,431
Shareholder servicing fees
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	19,017	19,106	57,533	55,618
Other
Disaggregation of Revenue [Line Items]
Revenue subject to contracts with customers	$ 4,293	$ 4,879	$ 15,827	$ 12,948