COMPUTATION OF EARNINGS PER COMMON SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Net income	$ 27,421	$ 23,138	$ 56,093	$ 50,091
Earnings Per Share, Basic and Diluted [Abstract]
Weighted average common shares-basic	41,765	42,810	41,692	42,751
Dilutive effect of employee equity incentive plans	740	787	868	916
Weighted average common shares-diluted	42,505	43,597	42,560	43,667
Basic earnings per common share	$ 0.66	$ 0.54	$ 1.35	$ 1.17
Diluted earnings per common share	$ 0.65	$ 0.53	$ 1.32	$ 1.15
Potentially dilutive securities excluded from diluted earnings per common share because their effect is anti-dilutive	392	183	409	162