SHARE-BASED COMPENSATION: Stock options outstanding and exercisable (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Stock options outstanding and exercisable by exercise price range
Options outstanding (in shares)	2,717,000
Options outstanding - Weighted-average remaining contractual life	5 years 8 months 25 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 13.45
Options exercisable (in shares)	2,109,993
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 13.53
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)	690,169
Options outstanding - Weighted-average remaining contractual life	6 years 4 months 8 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 1.68
Options exercisable (in shares)	474,434
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 1.77
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)	1,262,595
Options outstanding - Weighted-average remaining contractual life	4 years 10 months 12 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 14.94
Options exercisable (in shares)	1,076,909
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 14.47
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)	744,684
Options outstanding - Weighted-average remaining contractual life	6 years 7 months 16 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 21.31
Options exercisable (in shares)	539,098
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 21.33
Range of exercise price per share from $25.00 to $32.85
Stock options outstanding and exercisable by exercise price range
Exercise price per share, low end of range (in dollars per share)	25.00
Exercise price per share, high end of range (in dollars per share)	$ 32.85
Options outstanding (in shares)	19,552
Options outstanding - Weighted-average remaining contractual life	5 years 10 months 11 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 32.85
Options exercisable (in shares)	19,552
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 32.85
Stock options
Stock options outstanding and exercisable by exercise price range
Share-based compensation expense	$ 4.1	$ 5.4
Share-based compensation not yet recognized	$ 7.1
Period for recognition of unrecognized stock-based compensation expense	4 years