Commitments and Contingencies (Details)		3 Months Ended		9 Months Ended
		Sep. 30, 2015 USD ($) cowenfund	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) cowenfund	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Apr. 30, 2013 USD ($)
Lease Obligations
Net rent expense		$ 4,600,000	$ 4,300,000	$ 13,300,000	$ 12,500,000
Future minimum annual lease and service payments
Sublease income related to operating leases		500,000	$ 500,000	1,400,000	$ 1,300,000
Affiliated Entity
Future minimum annual lease and service payments
Other commitments, unfunded amount				9,600,000
Affiliated Entity | Healthcare Royalty Partners
Future minimum annual lease and service payments
Contractual obligation		45,400,000		45,400,000
Funding toward commitments				$ 36,000,000
Affiliated Entity | Healthcare Royalty Partners | Minimum
Future minimum annual lease and service payments
Expected call period				2 years
Affiliated Entity | Healthcare Royalty Partners | Maximum
Future minimum annual lease and service payments
Expected call period				5 years
Affiliated Entity | Starboard Leaders Fund LP
Future minimum annual lease and service payments
Funding toward commitments				$ 900,000
Affiliated Entity | Formation 8 Partners Fund I LP
Future minimum annual lease and service payments
Other commitments, unfunded amount				1,400,000
Affiliated Entity | Formation 8 Partners Hardware Fund I, L.P.
Future minimum annual lease and service payments
Other commitments, unfunded amount				1,100,000
Clawback Obligation
Future minimum annual lease and service payments
Contractual obligation		$ 6,200,000		$ 6,200,000		$ 6,200,000
Commitment to Invest | Affiliated Entity | Starboard Leaders Fund LP
Future minimum annual lease and service payments
Contractual obligation							$ 1,000,000
Commitment to Invest | Affiliated Entity | Formation 8 Partners Fund I LP
Future minimum annual lease and service payments
Term of capital commitment				1 year
Commitment to Invest | Affiliated Entity | Formation 8 Partners Hardware Fund I, L.P.
Future minimum annual lease and service payments
Term of capital commitment				1 year
Unfunded Commitments
Future minimum annual lease and service payments
Number of real estate investments, in investments | cowenfund		4		4
RCG Longview Partners II, LLC | Clawback Obligation
Future minimum annual lease and service payments
Contractual obligation		$ 6,200,000		$ 6,200,000		$ 6,200,000
Equipment Leases
Future minimum annual lease and service payments
Contractual Obligation, Due in remainder of current year	[1]	700,000		700,000
Contractual Obligation, Due in Second Year	[1]	2,502,000		2,502,000
Contractual Obligation, Due in Third Year	[1]	2,301,000		2,301,000
Contractual Obligation, Due in Fourth Year	[1]	2,221,000		2,221,000
Contractual Obligation, Due in Fifth Year	[1]	813,000		813,000
Thereafter	[1]	0		0
Future minimum annual lease and service payments	[1]	8,537,000		8,537,000
Service Payments
Future minimum annual lease and service payments
Contractual Obligation, Due in remainder of current year		4,490,000		4,490,000
Contractual Obligation, Due in Second Year		12,391,000		12,391,000
Contractual Obligation, Due in Third Year		6,245,000		6,245,000
Contractual Obligation, Due in Fourth Year		4,162,000		4,162,000
Contractual Obligation, Due in Fifth Year		1,375,000		1,375,000
Thereafter		0		0
Future minimum annual lease and service payments		28,663,000		28,663,000
Facility Leases
Future minimum annual lease and service payments
Contractual Obligation, Due in remainder of current year	[2]	5,094,000		5,094,000
Contractual Obligation, Due in Second Year	[2]	19,401,000		19,401,000
Contractual Obligation, Due in Third Year	[2]	16,030,000		16,030,000
Contractual Obligation, Due in Fourth Year	[2]	15,621,000		15,621,000
Contractual Obligation, Due in Fifth Year	[2]	14,822,000		14,822,000
Thereafter	[2]	47,064,000		47,064,000
Future minimum annual lease and service payments	[2]	$ 118,032,000		$ 118,032,000

[1] Equipment Leases include the Company's commitments relating to operating and capital leases. See Note 14 for further information on the capital lease minimum payments which are included in the table.

[2] The Company has entered into various agreements to sublease certain of its premises. The Company recorded sublease income related to these leases of $0.5 million and $0.5 million for the three months ended September 30, 2015 and 2014 and $1.4 million and $1.3 million for the nine months ended September 30, 2015 and 2014, respectively.