Investments - Schedule of Investments as a Percentage of Investments of Consolidated Funds (Additional Information) (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Cost of investments of Consolidated Funds	$ 21,987.8	$ 22,393.9
United States | Equity securities
Schedule of Investments [Line Items]
Cost of equity securities	833.0	1,337.9
United States | Partnership and LLC interests
Schedule of Investments [Line Items]
Cost of partnership and LLC interests	1,784.7	2,154.3
United States | Loans
Schedule of Investments [Line Items]
Cost of loans	83.6	260.7
United States | Total assets of the CLOs
Schedule of Investments [Line Items]
Cost of assets of the CLOs	11,658.3	10,413.0
Europe | Equity securities
Schedule of Investments [Line Items]
Cost of equity securities	650.2	939.1
Europe | Partnership and LLC interests
Schedule of Investments [Line Items]
Cost of partnership and LLC interests	694.3	840.9
Europe | Total assets of the CLOs
Schedule of Investments [Line Items]
Cost of assets of the CLOs	5,048.3	5,429.1
Global | Equity securities
Schedule of Investments [Line Items]
Cost of equity securities	77.0	85.6
Global | Partnership and LLC interests
Schedule of Investments [Line Items]
Cost of partnership and LLC interests	497.7	452.7
Global | Total assets of the CLOs
Schedule of Investments [Line Items]
Cost of assets of the CLOs	$ 643.7	$ 480.6