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, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Net income	$ 30,898	$ 31,552	$ 85,150	$ 82,927
Earnings Per Share, Basic and Diluted [Abstract]
Weighted average common shares-basic	42,541	47,649	44,623	47,621
Dilutive effect of employee equity incentive plans	1,099	1,782	1,234	1,650
Weighted average common shares-diluted	43,640	49,431	45,857	49,271
Earnings per common share-basic	$ 0.73	$ 0.66	$ 1.91	$ 1.74
Earnings per common share-diluted	$ 0.71	$ 0.64	$ 1.86	$ 1.68
Potentially dilutive securities excluded from earnings per common share-diluted because their effect is anti-dilutive	1,092	1,321	1,458	1,607