Segment Reporting - Reconciliation of Income Before Provision for Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Income before provision for income taxes	$ (158.1)	$ (529.1)	$ 474.1	$ 615.3	$ (197.1)	$ 175.4	$ 541.2	$ 472.4	$ 402.2	$ 991.9	$ 1,444.0
Other non-operating income									(7.4)	(30.3)	(16.5)
Net income attributable to non-controlling interests in Consolidated entities									(537.9)	(485.5)	(676.0)
Total Reportable Segments
Segment Reporting Information [Line Items]
Economic Net Income									396.6	962.4	1,285.2
Net performance fees									391.7	807.4	1,191.4
Investment income (loss)									(22.4)	(11.1)	(42.6)
Equity-based compensation									121.5	80.4	15.7
Reserve for litigation and contingencies									50.0	0.0	0.0
Fee Related Earnings									198.8	246.5	152.1
Realized performance fees, net of related compensation									788.5	732.8	674.5
Realized investment income (loss)									(64.8)	(6.1)	10.6
Distributable Earnings									922.5	973.2	837.2
Reconciling Items
Segment Reporting Information [Line Items]
Equity-based compensation issued in conjunction with the initial public offering, acquisitions and strategic investments									259.8	269.2	314.4
Acquisition related charges and amortization of intangibles and impairment									288.8	242.5	260.4
Other non-operating income									(7.4)	(30.3)	(16.5)
Tax expense associated with performance fee compensation									(14.9)	(25.3)	(34.9)
Net income attributable to non-controlling interests in Consolidated entities									(537.9)	(485.5)	(676.0)
Other adjustments									6.0	(0.1)	(6.2)
Net performance fees									$ 77.7	$ 5.9	$ (0.2)