Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Fund Management Fees
Period of time for which management fees will be received by partners from the initial closing date (in years)			10 years
Subsequent period in which management fees are recognized after these fees are called (in months)			6 months
Transaction and advisory fees	$ 4.8	$ 33.2	$ 12.4	$ 40.2
Performance Fees
Performance fees allocation percentage to partnership			20.00%
Accrued giveback obligations	221.8		$ 221.8		$ 104.4
Interest Income
Interest income of Consolidated Funds	$ 227.3	$ 214.8	$ 435.7	$ 436.0
Minimum
Fund Management Fees
Percentage of management fees earned			1.00%
Percentage of management fees earned on unrealized investments after termination of the investment period			0.60%
Extension period for fund closing (in years)			1 year
Percentage of management fees paid by hedge funds			1.50%
Percentage of management fees for business development companies			0.25%
Percentage of management fees for CLOs on the total par amount of assets in the fund			0.15%
Period of management fees related to Collateralized Loan Obligation (in years)			5 years
Percentage of management fees from fund of funds following the expiration of the weighted-average investment period			0.30%
Performance Fees
External coinvestment vehicles (as a percent)			10.00%
Percentage of allocation based performance fees related to fund of funds vehicles			2.00%
Percent of preferred returns			8.00%
Maximum
Fund Management Fees
Percentage of management fees earned			2.00%
Percentage of management fees earned on unrealized investments after termination of the investment period			2.00%
Extension period for fund closing (in years)			2 years
Percentage of management fees paid by hedge funds			2.00%
Percentage of management fees for business development companies			1.00%
Percentage of management fees for CLOs on the total par amount of assets in the fund			1.00%
Period of management fees related to Collateralized Loan Obligation (in years)			10 years
Percentage of management fees from fund of funds following the expiration of the weighted-average investment period			1.00%
Performance Fees
External coinvestment vehicles (as a percent)			20.00%
Percentage of allocation based performance fees related to fund of funds vehicles			10.00%
Percent of preferred returns			9.00%
Private Equity And Real Estate Fund | Minimum
Fund Management Fees
Percentage of management fees from funds of funds during the commitment fee period			0.30%
Private Equity And Real Estate Fund | Maximum
Fund Management Fees
Percentage of management fees from funds of funds during the commitment fee period			1.00%
Hedge funds | Minimum
Fund Management Fees
Percentage of management fees from funds of funds during the commitment fee period			0.20%
Hedge funds | Maximum
Fund Management Fees
Percentage of management fees from funds of funds during the commitment fee period			1.50%