RESTRUCTURING, IMPAIRMENT AND OTHER CHARGES: Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments	$ 233	$ 5,043	$ 1,890	$ 5,533
Restructuring reserve	5,000		5,000
Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			1,900			$ 3,000
Restructuring Activity 2019 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			7,700
Restructuring Activity 2018 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments					$ 2,700
Restructuring Activity 2015 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments							$ 9,300
Employee Severance | Restructuring Activity 2019
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	300		300
Employee Severance | Restructuring Activity 2018 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments					200
Employee Severance | Restructuring Activity 2015 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments							2,600
Termination Of Associates | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments						3,000
Termination Of Associates | Restructuring Activity 2019 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			(100)
Termination Of Associates | Restructuring Activity 2018 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			800		$ 2,500
Leased office facilities | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments						1,500
Adjustments to estimates related to the fiscal 2015 lease accruals | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments						$ 1,500
Contract Termination | Restructuring Activity 2015 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments							4,700
Leasehold Improvement Write Offs | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			800
Leasehold Improvement Write Offs | Restructuring Activity 2015 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments							$ 2,000
Asia-Pacific | Employee Severance | Restructuring Activity 2019
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			200
United States | Employee Severance | Restructuring Activity 2019
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			1,800
United States Australia China And Europe | Employee Severance | Restructuring Activity 2019
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			6,100
United States Australia China And Europe | Employee Severance | Restructuring Activity 2015
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 200		$ 200