Shares of Restricted Common Stock (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Price at Grant Date	$ 13.43
Number	41,500
Vesting Period (yrs.)	4 years
Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Price at Grant Date	$ 13.43	[1]
Number	41,500	[1]
Vesting Period (yrs.)	4 years	[1]

[1] Shares issued to certain of the Company's employees. These shares vest over four years with 25% vesting on the first anniversary of the grant date and the remainder vesting in equal quarterly installments thereafter.