SHARE-BASED COMPENSATION: (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Stock Option Activity - Number of Shares
Outstanding at beginning of the period (in shares)	3,033,071
Granted (in shares)	299,641
Exercised (in shares)	(396,912)
Forfeited or cancelled (in shares)	(63,540)
Outstanding at end of the period (in shares)	2,872,260
Exercisable at the end of the period (in shares)	2,174,071
Weighted-average exercise price per share
Outstanding at the beginning of the period (in dollars per share)	$ 13.14
Granted (in dollars per share)	21.32
Exercised (in dollars per share)	16.31
Forfeited or cancelled (in dollars per share)	20.20
Outstanding at the end of the period (in dollars per share)	13.40
Exercisable at the end of the period (in dollars per share)	$ 13.65
Weighted-average remaining contractual term
Weighted average remaining contractual term	6 years 20 days
Exercisable at the end of the period	5 years 4 months 23 days
Aggregate intrinsic value
Exercised	$ 4,039
Outstanding at the end of the period	32,439
Exercisable at the end of the period	$ 24,016
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)	34,500,000
Shares which remained available for future grants (in shares)	6,200,000
Amended and Restated 2005 Equity Compensation Plan [Member]
Share-based compensation
Shares which remained available for future grants (in shares)		32,900,000	28,400,000
Shares reserved for issuance	34,500,000		30,000,000