Equity - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended			1 Months Ended	12 Months Ended	1 Months Ended
	Mar. 31, 2011	Feb. 28, 2011	Dec. 31, 2012 Installment	Dec. 31, 2011	Jul. 10, 2012	Mar. 31, 2011 Installment Anniversary	Dec. 31, 2012 Installment Anniversary	Aug. 31, 2011 Installment Anniversary Non Employee Directors	Jan. 31, 2011 Installment Anniversary Non Employee Directors	Jan. 31, 2011 Time Based Restricted Stock Executive Officers	Jan. 31, 2011 Performance Based Restricted Stock Executive Officers
Equity [Line Items]
Noncontrolling common units			18,023,435
Percentage of ownership interests classified as noncontrolling			32.00%
Proceeds from private placement of common units		$ 5,400,000		$ 5,410,000
Common stock, shares issued		251,050
Shares of common stock			372,654
Preferred stock, shares authorized			10,000,000
Preferred stock, par-value			$ 0.01
Equity incentive award plan, common stock authorized for issuance			4,054,411
Equity incentive award plan, common stock available for future issuance			3,421,189
Performance period to which performance-based vesting is subject, years							3 years
Vesting installments of restricted shares			2
Equity incentive award plan, granted	123,950							1,957	1,951	198,000	297,000
Equity incentive award plan, fair value						1,600,000		40,000	200,000	4,100,000	3,900,000
Equity incentive award plan, forfeited									1,951
Restricted shares granted to members for board					8,015
Restricted stock granted			one-third
Restricted stock awards ratable vesting periods (First installment)			3
Noncash compensation expense			2,900,000	2,600,000
Unrecognized compensation expense			$ 4,400,000
Unrecognized compensation expense, weighted-average recognition period							1 year 7 months 6 days
Weighted average unvested shares outstanding			629,493	578,489