Changes in Non-Vested Shares of Restricted Common Stock (Detail) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of shares
Nonvested restricted common stock, beginning balance	114,505	139,641	357,522
Common stock vested	(96,172)	(98,530)	(356,886)
Common stock granted	255,151	73,394	139,005
Common stock forfeited	(14,161)
Nonvested restricted common stock, ending balance	259,323	114,505	139,641
Weighted Average Grant Date Fair Value per share
Nonvested restricted common stock, beginning balance	$ 4.94	$ 4.94	$ 4.32
Common stock vested	6.92	5.76	4.61
Common stock granted	6.89	9.89	5.70
Common stock forfeited	8.08
Nonvested restricted common stock, ending balance	$ 7.05	$ 4.94	$ 4.94