Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Other investments	$ 377,555	$ 373,344
General Partners Contribution to long-term incentive compensation plan	300	1,200	$ 1,600
Net receivable balance	11,100	12,000
AXA and its subsidiaries [Member]
Related Party Transaction [Line Items]
Sales of company-sponsored mutual funds	500,000	800,000	$ 1,100,000
AllianceBernstein Venture Fund I, L.P. [Member]
Related Party Transaction [Line Items]
Other investments	$ 100	$ 32,700
Ownership percentage	10.00%
Capital Accumulation Plan [Member]
Related Party Transaction [Line Items]
Awards granted	0
Term over which payments are to be received	10 years