STOCK-BASED COMPENSATION Stock Option Activity (Details) (Stock Options [Member], USD $) Share data in Thousands, except Per Share data, unless otherwise specified	6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at March 31, 2012	3,304
Options granted	266
Options exercised	(390)
Options forfeited or expired	(140)
Options outstanding at September 30, 2012	3,040
Weighted average exercise price of options outstanding, March 31, 2012	$ 26.47
Weighted average exercise price of options granted	$ 33.40
Weighted average exercise price of options exercised	$ 24.11
Weighted average exercise price of options forfeited or expired	$ 34.91
Weighted average exercise price of options outstanding, September 30, 2012	$ 27.00
Weighted average remaining contractual life of options outstanding at September 30, 2012	3 years 256 days
Aggregate intrinsic value of options outstanding at September 30, 2012	$ 26,109,000
Vested and expected to vest at September 30, 2012	3,005
Weighted average exercise price of options vested and expected to vest at September 30, 2012	$ 26.91
Weighted average remaining contractual life of options vested and expected to vest at September 30, 2012	3 years 219 days
Aggregate intrinsic value of options vested and expected to vest at September 30, 2012	26,038,000
Exercisable at September 30, 2012	2,200
Weighted average exercise price of options exercisable at September 30, 2012	$ 24.45
Weighted average remaining contractual life of options exercisable at September 30, 2012	2 years 292 days
Aggregate intrinsic value of options exercisable at September 30, 2012	24,183,000
Total intrinsic value of options exercised	4,500,000	11,700,000
Total cash received as a result of stock option exercises	9,400,000
Total unrecognized compensation cost related to unvested stock options	$ 7,900,000
Period of recognition for unrecognized compensation cost related to unvested stock options	2 years