Segment Reporting - Total Segments to Partnership Income Before Provision for Taxes Reconciliation (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
Expenses	802.5	795.3	843.6	1,027.0	928.7	705.1	1,042.6	1,099.0	3,468.4	3,775.4	3,693.9
Other income	(71.4)	$ (31.3)	$ 461.6	$ 505.5	(107.5)	$ 125.5	$ 445.0	$ 424.0	864.4	887.0	696.7
Economic net income									402.2	991.9	1,444.0
Total assets	32,191.0				35,994.3				32,191.0	35,994.3	35,622.3
Total Reportable Segments
Segment Reporting Information [Line Items]
Revenues									2,132.4	3,022.0	3,368.9
Expenses									1,735.8	2,059.6	2,083.7
Other income									0.0	0.0	0.0
Economic net income									396.6	962.4	1,285.2
Total assets	6,114.0				7,397.4				6,114.0	7,397.4
Consolidated Funds
Segment Reporting Information [Line Items]
Revenues									975.5	956.0	1,043.1
Expenses									1,258.8	1,286.5	1,169.4
Other income									886.9	898.4	701.3
Economic net income									603.6	567.9	575.0
Total assets	26,395.7				28,809.8				26,395.7	28,809.8
Reconciling Items
Segment Reporting Information [Line Items]
Revenues									(101.7)	(97.7)	29.2
Expenses									473.8	429.3	440.8
Other income									(22.5)	(11.4)	(4.6)
Economic net income									(598.0)	(538.4)	$ (416.2)
Total assets	$ (318.7)				$ (212.9)				$ (318.7)	$ (212.9)