Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended			1 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Cash	Dec. 31, 2012 New York	Sep. 30, 2013 San Francisco Lease One	Sep. 30, 2013 San Francisco Lease Two	Sep. 30, 2013 San Francisco Lease Three
Commitments and Contingencies [Line Items]
Lease agreement commencement date							Apr. 01, 2011	Jul. 01, 2012	May 01, 2013
Lease agreement expiration date						Jan. 31, 2014	Jun. 01, 2017	Jun. 01, 2015	Jun. 01, 2017
Lease agreement renewal term						1 year		2 years
Lease agreement extended expiration date								Jun. 01, 2017
Rental expense	$ 500,000	$ 100,000	$ 1,300,000	$ 400,000
Security deposit made under lease agreement					200,000
Security deposit made under lease agreement	200,000		200,000
Investment commitments of loan	10,000		10,000
Maximum cash pledged	5,000,000		5,000,000
Pledged and restricted to support contingent obligation	$ 3,400,000		$ 3,400,000