Computation of Basic and Diluted Earnings Per Share (Detail) (USD $)	3 Months Ended								12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2013	Mar. 31, 2012
Basic
Net earnings	$ 1,249,571	$ 1,150,058	$ 1,644,329	$ 2,091,854	$ 2,204,896	$ 1,799,249	$ 2,314,908	$ 1,831,411	$ 6,135,812	$ 8,150,464
Weighted average common shares									6,799,444	6,799,444
Dilutive
Net earnings	$ 1,249,571	$ 1,150,058	$ 1,644,329	$ 2,091,854	$ 2,204,896	$ 1,799,249	$ 2,314,908	$ 1,831,411	$ 6,135,812	$ 8,150,464
Weighted average common shares and common share equivalents									6,799,444	6,799,444