Segment Reporting - Consolidated Revenues and Assets Based on Geographical Focus of Associated Investment Vehicle (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]
Revenues	$ 715.8	$ 297.5	$ 856.1	$ 1,136.8	$ 839.1	$ 755.0	$ 1,138.8	$ 1,147.4	$ 3,006.2	$ 3,880.3	$ 4,441.2
Percentages Of Revenue By Geographic Regions									100.00%	100.00%	100.00%
Assets	32,191.0				35,994.3				$ 32,191.0	$ 35,994.3	$ 35,622.3
Percentage Of Assets By Geographic Regions									100.00%	100.00%	100.00%
Americas
Segment Reporting Information [Line Items]
Revenues									$ 1,518.7	$ 2,283.3	$ 2,613.0
Percentages Of Revenue By Geographic Regions									51.00%	59.00%	59.00%
Assets	19,059.3				20,986.9				$ 19,059.3	$ 20,986.9	$ 19,091.7
Percentage Of Assets By Geographic Regions									59.00%	58.00%	53.00%
EMEA
Segment Reporting Information [Line Items]
Revenues									$ 1,090.1	$ 1,527.3	$ 1,459.3
Percentages Of Revenue By Geographic Regions									36.00%	39.00%	33.00%
Assets	12,368.7				14,446.4				$ 12,368.7	$ 14,446.4	$ 15,974.6
Percentage Of Assets By Geographic Regions									39.00%	40.00%	45.00%
Asia Pacific
Segment Reporting Information [Line Items]
Revenues									$ 397.4	$ 69.7	$ 368.9
Percentages Of Revenue By Geographic Regions									13.00%	2.00%	8.00%
Assets	$ 763.0				$ 561.0				$ 763.0	$ 561.0	$ 556.0
Percentage Of Assets By Geographic Regions									2.00%	2.00%	2.00%