Related Party Transactions - Summary of Revenues, Expenses and Balance Sheet Items for AXA and Subsidiaries (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Investment advisory and services fees	$ 1,933,471	$ 1,973,837	$ 1,958,250
Bernstein research services	479,875	493,463	482,538
Distribution revenues	384,405	427,156	444,970
Other revenues	110,096	101,169	108,788
Total revenues	3,037,902	3,024,048	3,007,792
Expenses:
Commissions and distribution payments to financial intermediaries	371,607	393,033	413,054
General and administrative	426,147	431,635	426,960
Other	208,538	223,415	224,576
Total expenses	2,305,614	2,389,628	2,396,745
Balance Sheet:
Institutional investment advisory and services fees receivable	270,373	257,091
AXA and its subsidiaries [Member]
Revenues:
Investment advisory and services fees	150,016	149,035	131,317
Bernstein research services	583	694	958
Distribution revenues	12,145	11,541	11,590
Other revenues	969	912	1,066
Total revenues	163,713	162,182	144,931
Expenses:
Commissions and distribution payments to financial intermediaries	16,077	16,140	16,255
General and administrative	16,315	17,680	20,176
Other	1,653	1,483	1,457
Total expenses	34,045	35,303	$ 37,888
Balance Sheet:
Institutional investment advisory and services fees receivable	11,826	12,622
Prepaid expenses	1,461	1,431
Other due to AXA and its subsidiaries	(5,325)	(6,231)
Total	$ 7,962	$ 7,822