Quarterly report pursuant to Section 13 or 15(d)

Mandatorily Redeemable Preferred Stock - Additional Information (Detail)

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Mandatorily Redeemable Preferred Stock - Additional Information (Detail) (USD $)
 1 Months Ended 1 Months Ended 1 Months Ended 6 Months Ended
Feb. 29, 2012
Jun. 30, 2013
Dec. 31, 2012
Feb. 29, 2012
Mandatorily Redeemable Preferred Stock [Member]
Jun. 30, 2013
Mandatorily Redeemable Preferred Stock [Member]
Jun. 28, 2013
Mandatorily Redeemable Preferred Stock [Member]
Feb. 29, 2012
Series C Preferred Stock [Member]
Jun. 30, 2013
Series C Preferred Stock [Member]
Class of Stock [Line Items]                
Public offering of Preferred Stock   2,150,000 2,150,000 1,540,000        
Series C Preferred Stock             7.125% 7.125%
Preferred Stock, par value   $ 0.001 $ 0.001 $ 0.001        
Public offering price       $ 25.00        
Gross proceeds of the offering totaled       $ 38,500,000        
Net proceeds, after deducting offering expenses       36,700,000        
Preferred shares at a redemption price $ 25.00              
Preferred Stock redemption term On or after January 31, 2016, we may redeem the shares at a redemption price of $25.00 per share, plus any accumulated and unpaid dividends to and including the date of redemption.              
Preferred Stock mandatory redemption date Jan. 31, 2017              
Deferred financing costs 1,800,000              
Fair value of Term Preferred Stock   38,500,000 38,500,000   38,500,000      
Carrying value Term Preferred Stock   $ 2,000 $ 2,000   $ 38,500,000      
Closing price of Term Preferred Stock           $ 25.03