Summary of Significant Accounting Policies - Additional Information (Details) € in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 EUR (€)	Dec. 31, 2014 USD ($)
Accounting Policies [Abstract]
Accrued performance fee-related compensation	$ 1,525.3		$ 1,525.3			$ 1,815.4
Percentage of estimated realizable tax benefit to be paid by corporate taxpayers on exchange transactions			85.00%
Percentage of remaining estimated realizable tax benefit on exchange transactions			15.00%
Cash withheld from carried interest distributions for potential giveback obligations	19.7		$ 19.7			29.9
Cash received on behalf of a non-consolidated funds	11.9		11.9			8.7
Restricted cash included in escrow related to tax contingency					€ 4.4	5.4
Restricted cash for carried interest proceeds for one corporate private equity fund						13.2
Amount included in restricted cash related to a fund’s pending sale			247.7
Cash received to satisfy collateral requirements	1.9		1.9			2.3
Restricted securities of consolidated funds	16.5		16.5			12.6
Foreign currency transaction gain (losses) before tax	9.9	$ 1.1	8.6	$ 5.6
Partners’ capital appropriated for Consolidated Funds	$ 158.0		$ 158.0			$ 184.5