Segment Reporting - Reconciliation of Income Before Provision for Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Income before provision for income taxes	$ 11.9	$ (49.7)	$ 67.8	$ 15.3	$ (158.1)	$ (529.1)	$ 474.1	$ 615.3	$ 45.3	$ 402.2	$ 991.9
Other non-operating income									(11.2)	(7.4)	(30.3)
Net income attributable to non-controlling interests in Consolidated entities									(41.0)	(537.9)	(485.5)
Net performance fees									398.7	314.0	801.5
Investment income (loss)									154.6	0.5	(14.9)
Reconciling Items
Segment Reporting Information [Line Items]
Equity-based compensation issued in conjunction with the initial public offering, acquisitions and strategic investments									223.4	259.8	269.2
Acquisition related charges and amortization of intangibles and impairment									94.2	288.8	242.5
Other non-operating income									(11.2)	(7.4)	(30.3)
Tax provision associated with performance fees									(15.1)	(14.9)	(25.3)
Net income attributable to non-controlling interests in Consolidated entities									(41.0)	(537.9)	(485.5)
Severance and other adjustments									10.3	6.0	(0.1)
Net performance fees									(5.0)	77.7	5.9
Total Reportable Segments
Segment Reporting Information [Line Items]
Economic Net Income									305.9	396.6	962.4
Net performance fees									393.7	391.7	807.4
Investment income (loss)									50.3	(22.4)	(11.1)
Equity-based compensation									119.6	121.5	80.4
Reserve for litigation and contingencies									0.0	50.0	0.0
Fee Related Earnings									(18.5)	198.8	246.5
Realized performance fees, net of related compensation									625.3	788.5	732.8
Realized investment income (loss)									44.9	(64.8)	(6.1)
Distributable Earnings									$ 651.7	$ 922.5	$ 973.2