SHARE-BASED COMPENSATION: Stock options outstanding and exercisable (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Stock options outstanding and exercisable by exercise price range
Options outstanding (in shares)	3,200,503
Options outstanding - Weighted-average remaining contractual life	5 years 10 months 24 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 13.85
Options exercisable (in shares)	2,412,279
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 14.49
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)	801,586
Options outstanding - Weighted-average remaining contractual life	7 years 1 month 6 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 1.67
Options exercisable (in shares)	460,516
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 1.71
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)	1,396,449
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)	$ 15.10
Options exercisable (in shares)	1,184,653
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 14.62
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)	982,916
Options outstanding - Weighted-average remaining contractual life	6 years
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 21.62
Options exercisable (in shares)	752,447
Options exercisable - Weighted-average exercise price per share (in dollars per share)	$ 21.74
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	6 years 4 months 24 days
Options outstanding - Weighted-average exercise price per share (in dollars per share)	$ 32.85
Options exercisable (in shares)	14,663
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	$ 1.4	$ 1.8
Share-based compensation not yet recognized	$ 10.2
Period for recognition of unrecognized stock-based compensation expense	4 years