SHARE-BASED COMPENSATION: (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Stock Option Activity - Number of Shares
Outstanding at beginning of the period (in shares)	3,604,102
Exercised (in shares)	(498,180)
Forfeited or cancelled (in shares)	(47,833)
Outstanding at end of the period (in shares)	3,058,089
Exercisable at the end of the period (in shares)	2,353,864
Weighted-average exercise price per share
Outstanding at the beginning of the period (in dollars per share)	$ 14.52
Exercised (in dollars per share)	13.82
Forfeited or cancelled (in dollars per share)	16.24
Outstanding at the end of the period (in dollars per share)	14.60
Exercisable at the end of the period (in dollars per share)	$ 14.49
Weighted-average remaining contractual term
Outstanding at the end of the period	5 years 4 months 24 days
Exercisable at the end of the period	4 years 7 months 6 days
Aggregate intrinsic value
Exercised	$ 4,848
Outstanding at the end of the period	36,961
Exercisable at the end of the period	$ 28,685
Stock Appreciation Right
Share-based compensation
Period for recognition of unrecognized stock-based compensation expense	5 years
Stock Option and Equity Compensation Plans
Share-based compensation
Total shares reserved for issuance since inception of the stock option and equity compensation plans (in shares)	28,900,000
Shares which remained available for future grants (in shares)	2,200,000
Stock options
Share-based compensation
Share-based compensation expense	$ 3,500	$ 5,900
Future share-based compensation expense	$ 6,100
Period for recognition of unrecognized stock-based compensation expense	4 years
Stock Appreciation Rights (SARs)
Share-based compensation
Share-based compensation expense	$ 100	$ 100
Weighted-average remaining contractual term
Exercisable at the end of the period	0 years