RESTRUCTURING, IMPAIRMENT AND OTHER CHARGES: Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments	$ 3,660	$ 929	$ 3,562	$ 1,208
Deferred rent credit	1,400		1,400
Accrued Rent	2,400		2,400
Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			3,600		$ 8,900
Restructuring Activity2016 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments						$ 12,000
Restructuring Activity2015 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments							$ 21,800
Employee Severance | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			300		3,800
Employee Severance | Restructuring Activity2016 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments						8,600
Employee Severance | Restructuring Activity2015 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments							13,300
Termination Of Associates | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			1,000		3,000
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
Lease agreements | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			2,500
Contract Termination | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments							6,500
Contract Termination | Restructuring Activity2016 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments						3,000
Contract Termination | Restructuring Activity2015
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	800		800
Contract Termination | Restructuring Activity2015 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments							6,500
Leasehold Improvement Write Offs | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			1,100		$ 2,100
Leasehold Improvement Write Offs | Restructuring Activity2016 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments						400
Leasehold Improvement Write Offs | Restructuring Activity2015 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments							2,000
UNITED STATES | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			400
UNITED STATES | Employee Severance | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			1,500
United States Australia Europe And Brazil | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments	300
United States Australia Europe And Brazil | Employee Severance | Restructuring Activity2016
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments						8,600
France | Restructuring Activity2015 | Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments						$ 3,000
United States Australia China And Europe | Employee Severance | Restructuring Activity2015
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments							$ 13,300
Restructuring reserve	$ 300		$ 300