Related Party Transactions - Summary of Revenues, Expenses and Balance Sheet Items for AXA and Subsidiaries (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Investment advisory and services fees	$ 1,973,837	$ 1,958,250	$ 1,849,105
Bernstein research services	493,463	482,538	445,083
Distribution revenues	427,156	444,970	465,424
Other revenues	101,169	108,788	105,058
Total revenues	3,024,048	3,007,792	2,917,971
Expenses:
Commissions and distribution payments to financial intermediaries	393,033	413,054	426,824
General and administrative	431,635	426,960	423,043
Other	223,415	224,576	204,568
Total expenses	2,389,628	2,396,745	2,350,796
Balance Sheet:
Institutional investment advisory and services fees receivable	257,091	292,901
AXA and its subsidiaries [Member]
Revenues:
Investment advisory and services fees	149,035	131,317	129,937
Bernstein research services	694	958	1,152
Distribution revenues	11,541	11,590	9,823
Other revenues	887	1,041	815
Total revenues	162,157	144,906	141,727
Expenses:
Commissions and distribution payments to financial intermediaries	16,140	16,255	13,338
General and administrative	17,680	20,176	18,311
Other	1,483	1,457	1,425
Total expenses	35,303	37,888	$ 33,074
Balance Sheet:
Institutional investment advisory and services fees receivable	12,622	9,681
Prepaid expenses	1,431	1,483
Other due to AXA and its subsidiaries	(6,231)	(5,510)
Total	$ 7,822	$ 5,654