RESTRUCTURING, IMPAIRMENT AND OTHER CHARGES: Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments	$ (18)	$ 899	$ 3,545	$ 2,107
Deferred rent credit	1,400		1,400
Accrued Rent	2,100		2,100
Gains Losses And Other Items Net
Restructuring Cost and Reserve [Line Items]
Restructuring charges and adjustments			3,500		$ 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			200		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			2,300
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			300
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	200
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