COMPUTATION OF EARNINGS PER COMMON SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Net income	$ 28,206	$ 30,898	$ 77,693	$ 85,150
Earnings Per Share, Basic and Diluted [Abstract]
Weighted average common shares-basic	41,745	42,541	41,629	44,623
Dilutive effect of employee equity incentive plans	873	1,099	950	1,234
Weighted average common shares-diluted	42,618	43,640	42,579	45,857
Basic earnings per common share	$ 0.68	$ 0.73	$ 1.87	$ 1.91
Diluted earnings per common share	$ 0.66	$ 0.71	$ 1.82	$ 1.86
Potentially dilutive securities excluded from diluted earnings per common share because their effect is anti-dilutive	1,210	1,092	1,125	1,458