Business Segment Information - Net Revenues Derived From Investment Management, Research and Related Services (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financial Services Revenue [Abstract]
Total revenues									$ 3,323,686	$ 3,037,902	$ 3,024,048
Less: Interest expense									25,165	9,123	3,321
Net revenues	$ 919,141	$ 812,150	$ 802,313	$ 764,917	$ 786,256	$ 747,591	$ 725,806	$ 769,126	3,298,521	3,028,779	3,020,727
Institutions [Member]
Financial Services Revenue [Abstract]
Total revenues									476,235	422,060	435,205
Retail [Member]
Financial Services Revenue [Abstract]
Total revenues									1,423,891	1,261,907	1,362,541
Private Wealth Management [Member]
Financial Services Revenue [Abstract]
Total revenues									787,362	711,599	689,853
Bernstein Research Services [Member]
Financial Services Revenue [Abstract]
Total revenues									449,919	479,875	493,463
Other Services [Member]
Financial Services Revenue [Abstract]
Total revenues									$ 186,279	$ 162,461	$ 42,986