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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Total revenues									$ 3,419,760	$ 3,323,686	$ 3,037,902
Less: Interest expense									52,399	25,165	9,123
Net revenues	$ 804,660	$ 850,176	$ 844,738	$ 867,787	$ 919,141	$ 812,150	$ 802,313	$ 764,917	3,367,361	3,298,521	3,028,779
Institutions
Revenues:
Total revenues									479,068	477,140	422,060
Retail
Revenues:
Total revenues									1,494,445	1,423,890	1,261,907
Private Wealth Management
Revenues:
Total revenues									883,234	787,362	711,599
Bernstein Research Services
Revenues:
Total revenues									439,432	449,919	479,875
Other
Revenues:
Total revenues									$ 123,581	$ 185,375	$ 162,461