Quarterly Results (Unaudited) - Summary of Unaudited Quarterly Results of Operations (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 128,294,000	$ 123,891,000	$ 124,460,000	$ 126,939,000	$ 122,195,000	$ 122,352,000	$ 123,714,000	$ 124,364,000	$ 503,584,000	$ 492,625,000	$ 478,816,000
Gross Profit	26,445,000	25,232,000	26,684,000	26,183,000	22,674,000	24,128,000	25,467,000	27,700,000	104,544,000	99,969,000	108,481,000
Net income	$ 6,667,000	$ 6,691,000	$ 8,267,000	$ 6,900,000	$ 5,576,000	$ 6,832,000	$ 7,883,000	$ 8,299,000	$ 28,525,000	$ 28,590,000	$ 34,392,000
Net Income per Basic Common Share	$ 0.34	$ 0.34	$ 0.42	$ 0.34	$ 0.27	$ 0.33	$ 0.38	$ 0.40	$ 1.44	$ 1.38	$ 1.63
Net Income per Diluted Common Share	$ 0.34	$ 0.34	$ 0.41	$ 0.34	$ 0.27	$ 0.33	$ 0.37	$ 0.39	$ 1.43	$ 1.37	$ 1.61