Dividend Reinvestment Plan - Additional Information (Detail) - Dividend Reinvestment Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Jul. 20, 2012
Dividend Reinvestment Plan
Common shares to be issued			2,000,000
Minimum percentage of cash dividends	25.00%
Maximum additional cash purchase of common shares per fiscal quarter	$ 5
Percentage estimated value for dividend reinvestments	95.00%
Percentage estimated value for additional optional cash purchases	100.00%
Estimated value per common share	$ 15.50	$ 15.00
Purchase price per common share for dividend reinvestments	14.725	14.25
Purchase price per common share additional optional cash purchases	$ 15.50	$ 15.00
Notice period to participants	10 days
Shares issued pursuant to dividend reinvestments	284,000	231,000
Shares were issued pursuant to additional optional cash purchases under the plan	116,000	128,000