SHARE-BASED COMPENSATION: (Details) $ / shares in Units, $ in Thousands		6 Months Ended
	Aug. 18, 2015 shares	Sep. 30, 2015 USD ($) multiple $ / shares shares	Sep. 30, 2014 USD ($)
Stock Option Activity - Number of Shares
Outstanding at the beginning of the period (in shares)		4,870,219
Granted (in shares)		445,785
Exercised (in shares)		(438,979)
Forfeited or cancelled (in shares)		(693,809)
Outstanding at the end of the period (in shares)		4,183,216
Exercisable at the end of the period (in shares)		2,858,695
Weighted-average exercise price per share
Outstanding at the beginning of the period (in dollars per share) | $ / shares		$ 15.10
Granted (in dollars per share) | $ / shares		17.84
Exercised (in dollars per share) | $ / shares		10.16
Forfeited or cancelled (in dollars per share) | $ / shares		25.71
Outstanding at the end of the period (in dollars per share) | $ / shares		14.15
Exercisable at the end of the period (in dollars per share) | $ / shares		$ 14.72
Weighted-average remaining contractual term
Outstanding at the end of the period		5 years 2 months 16 days
Exercisable at the end of the period		3 years 8 months 19 days
Aggregate intrinsic value
Exercised | $		$ 3,012
Outstanding at the end of the period | $		27,586
Exercisable at the end of the period | $		$ 17,874
Stock Option and Equity Compensation Plans
Share-based compensation
Aggregate number of shares reserved for issuance under equity compensation plans since the inception of such plans (in shares)	28,900,000	24,800,000
Shares which remained available for future grants (in shares)		5,700,000
Additional number of shares reserved for issuance under equity compensation plans (in shares)	4,100,000
Stock options
Share-based compensation
Granted (in shares)		445,785
Per-share weighted-average fair value of the stock options granted (in dollars per share) | $ / shares		$ 6.48
Pricing model used for share-based compensation arrangement		binomial lattice
Dividend yield (as a percent)		0.00%
Risk-free interest rate (as a percent)		2.20%
Expected option life		4 years 6 months
Expected volatility (as a percent)		40.00%
Suboptimal exercise multiple | multiple		1.4
Share-based compensation expense | $		$ 5,900	$ 3,900
Future share-based compensation expense expected | $		$ 13,600
Period for recognition of unrecognized stock-based compensation expense		4 years