Series C Convertible Preferred Stock - Additional Information (Detail) (USD $)			1 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	May 31, 2013 Series C Convertible Preferred Stock	Mar. 31, 2011 Series C Convertible Preferred Stock	Mar. 31, 2013 Series C Convertible Preferred Stock	Jun. 30, 2013 Series C Convertible Preferred Stock Installment
Preferred Stock [Line Items]
Preferred shares issued				7,000
Initial stated value per preferred share				$ 10,000
Net proceeds from sale of shares				$ 64,013,000
Agent fees and offering costs				5,987,000
Percentage of dividend payable						8.00%
Number of equal quarterly installments						9
Installments start date						Sep. 01, 2011
Installments end date						Sep. 01, 2013
Preferred share plus accumulated and unpaid dividends						$ 10,000
Conversion price of convertible preference stock			$ 15.83		$ 15.83
Conversion share of convertible preference stock			650		165
Issuance of common stock related to conversion of preferred stock			418,000		105,000
Preferred stock shares outstanding						739
Common Stock, shares outstanding	34,052,503	29,818,225				467,000