Related Party Transactions - Additional Information 1 (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Related Party Transaction [Line Items]
General and administrative expenses	$ 2,742,000	$ 2,291,000	$ 5,178,000	$ 3,948,000
MMI [Member]
Related Party Transaction [Line Items]
Compensation and benefit costs, net	7,173,000		8,397,000
Accrued and unpaid reimbursable compensation and benefit costs	748,000		748,000
Sponsor [Member]
Related Party Transaction [Line Items]
General and administrative expenses	$ 0	$ 2,276,000	$ 993,000	$ 3,929,000