Stock Based Compensation and Stock Options - Stock Options (Detail) (USD $)	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding, beginning, Shares	1,199,630	1,303,806	1,100,952	1,502,646
Options granted, Shares	48,100	41,100	240,000	63,400
Options exercised, Shares	(53,279)	(72,212)	(119,051)	(203,358)
Options cancelled, Shares	(3,200)	(8,164)	(30,650)	(98,158)
Options outstanding, ending, Shares	1,191,251	1,264,530	1,191,251	1,264,530
Options outstanding, beginning, Average Price	$ 19.60	$ 17.30	$ 18.65	$ 17.10
Options granted, Average Price	$ 34.77	$ 22.07	$ 25.73	$ 21.53
Options exercised, Average Price	$ 15.62	$ 12.28	$ 14.45	$ 12.57
Options cancelled, Average Price	$ 19.72	$ 22.53	$ 23.07	$ 21.54
Options outstanding, ending, Average Price	$ 20.39	$ 17.71	$ 20.39	$ 17.71