INCOME TAXES: - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Balance at beginning of period	$ 12,870	$ 10,906	$ 9,711
Increases related to prior year tax positions	1,134	307	1,717
Decreases related to prior year tax positions	208	466	1,227
Increases related to current year tax positions	3,172	2,123	2,035
Settlements with taxing authorities	0	0	(1,330)
Lapse of statute of limitations	(1,553)	0	0
Balance at end of period	$ 15,415	$ 12,870	$ 10,906