STOCK-BASED COMPENSATION: Stock options outstanding and exercisable (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Stock options outstanding and exercisable by exercise price range
Options outstanding (in shares)	1,347,709
Options outstanding - Weighted-average remaining contractual life	4 years 2 months 12 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 15.00
Options exercisable (in shares)	1,278,265
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 15.73
Range of exercise price per share from $0.61 to $9.99
Stock options outstanding and exercisable by exercise price range
Exercise price per share, low end of range (in dollars per share)	0.61
Exercise price per share, high end of range (in dollars per share)	$ 9.99
Options outstanding (in shares)	192,826
Options outstanding - Weighted-average remaining contractual life	5 years 1 month 6 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 1.53
Options exercisable (in shares)	123,382
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 1.57
Range of exercise price per share from $10.00 to $19.99
Stock options outstanding and exercisable by exercise price range
Exercise price per share, low end of range (in dollars per share)	10.00
Exercise price per share, high end of range (in dollars per share)	$ 19.99
Options outstanding (in shares)	709,672
Options outstanding - Weighted-average remaining contractual life	3 years 3 months 18 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 14.69
Options exercisable (in shares)	709,672
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 14.69
Range of exercise price per share from $20.00 to $24.99
Stock options outstanding and exercisable by exercise price range
Exercise price per share, low end of range (in dollars per share)	20.00
Exercise price per share, high end of range (in dollars per share)	$ 24.99
Options outstanding (in shares)	445,211
Options outstanding - Weighted-average remaining contractual life	5 years 2 months 12 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 21.32
Options exercisable (in shares)	445,211
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 21.32
Stock options
Stock options outstanding and exercisable by exercise price range
Share-based compensation expense	$ 0.7	$ 1.0
Share-based compensation not yet recognized	$ 1.9