COMPUTATION OF EARNINGS PER COMMON SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 26,953	$ 23,563
Earnings Per Share, Basic and Diluted [Abstract]
Weighted average common shares-basic	42,692	41,660
Dilutive effect of employee equity incentive plans	958	910
Weighted average common shares-diluted	43,650	42,570
Basic earnings per common share	$ 0.63	$ 0.57
Diluted earnings per common share	$ 0.62	$ 0.55
Potentially dilutive securities excluded from diluted earnings per common share because their effect is anti-dilutive	292	1,100