Fair Value - Additional Information (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2015 USD ($) investment contingent_consideration_liability	Dec. 31, 2014 USD ($) investment	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers out of level 2					$ 4,000,000	$ 3,000,000
Transfers out of level 3	$ 26,000	$ 1,600,000
Non-controlling interest ownership percentage			90.00%
Contingent payment arrangements			$ 0	$ 9,365,000			$ 17,100,000
Changes in estimates			7,211,000	4,375,000
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements			$ 31,399,000	42,436,000
Consolidated Private Equity Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Ownership percentage			10.00%
Private Equity Healthcare and Cleantech [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investment				$ 200,000
Number of investments | investment				2
Cost-method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of private equity investments | investment			1
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of contingent consideration liabilities | contingent_consideration_liability			3
Changes in estimates			$ 7,200,000	$ 4,400,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements			$ 31,399,000	42,436,000
Fair Value, Inputs, Level 3 [Member] | Consolidated Private Equity Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of private equity investments owned by consolidated venture capital fund			20.00%
Fair Value, Inputs, Level 3 [Member] | Private Equity Investment Venture Capital Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investment			$ 6,500,000	7,500,000
Fair Value, Inputs, Level 3 [Member] | Private Equity Technology Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investment in venture capital fund			32,000,000	31,000,000
Unfunded commitment			2,900,000	$ 2,900,000
Investment in venture capital fund, description				communications, consumer, digital media, healthcare and information technology markets
Fair Value, Inputs, Level 3 [Member] | Private Equity Technology Media and Telecommunications [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate				18.00%
Fair Value, Inputs, Level 3 [Member] | Consolidated Private Equity Investment Venture Capital Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investment in venture capital fund			100,000	$ 100,000
Unfunded commitment			0	0
Fair Value, Inputs, Level 3 [Member] | Contingent Payment Arrangements [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements			$ 31,400,000	$ 42,400,000
Fair Value, Inputs, Level 3 [Member] | Contingent Payment Arrangements [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AUM growth rates weighted average			46.00%
Revenue growth rate			43.00%
Fair Value, Inputs, Level 3 [Member] | Contingent Payment Arrangements [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate			3.00%