Equity and EPS - The Computations of Basic and Diluted Earnings (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operations:
Net Income (Loss)	$ 8,285	$ 9,532	$ 6,308	$ 7,059	$ 6,479	$ 6,771	$ 7,871	$ 5,070	$ 31,184	$ 26,191	$ 23,675
Less: Amounts allocated to participating securities (non-vested shares and units)									954	873	832
Net income attributable to common shareholders and used in earnings per share calculation (Note 6)									$ 30,230	$ 25,318	$ 22,843
Share information:
Basic weighted average common shares (in Shares)									16,643,811	17,123,556	17,305,866
Incremental shares from potential dilutive securities (in Shares)									0	0	0
Diluted weighted average common shares (in Shares)									16,643,811	17,123,556	17,305,866
Basic and diluted earnings per share (in dollars per share)	$ 0.48	$ 0.55	$ 0.37	$ 0.41	$ 0.38	$ 0.38	$ 0.44	$ 0.28	$ 1.82	$ 1.48	$ 1.32