Business Combinations - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jun. 01, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Business Acquisition [Line Items]
Total operating expenses		$ 105,624	$ 90,948	$ 212,035	$ 160,677
Employment expenses		$ 54,868	$ 42,992	115,564	$ 82,633
Purchase price, cash				$ 471,400
RidgeWorth
Business Acquisition [Line Items]
Assets under management	$ 40,100,000
Long term assets under management	35,700,000
Liquidity strategy assets under management	4,400,000
Purchase price	547,100
Consolidated entity excluding consolidated investment products | RidgeWorth
Business Acquisition [Line Items]
Purchase price	485,200
CLOs | RidgeWorth
Business Acquisition [Line Items]
Purchase price	$ 61,900