TOPIC 606 ADOPTION IMPACT AND REVENUE FROM CONTRACTS WITH CUSTOMERS: Impact of changes in accounting policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Apr. 01, 2018	Mar. 31, 2018
ASSETS
Trade accounts receivable, net	$ 163,767			$ 167,188
Refundable income taxes	11,761			9,733
Deferred income taxes	11,488			12,225
Deferred commissions, net	18,137			0
Others	961,815
TOTAL ASSETS	1,166,968			1,209,253
Liabilities
Deferred revenue	31,621			31,720
Deferred income taxes	42,258			40,243
Other liabilities	371,033
Total liabilities	444,912
Equity
Retained earnings	638,043			628,331
Other equity	84,013
Total equity	722,056			749,095
TOTAL LIABILITIES AND EQUITY	1,166,968			$ 1,209,253
Income Statement [Abstract]
Revenues	226,960	$ 212,514
Cost of revenue	117,271	113,960
Gross profit	109,689	98,554
Operating expenses:
Sales and marketing	54,850	48,440
Other operating expenses	60,540
Total operating expenses	115,390	104,261
Loss from operations	(5,701)	(5,707)
Total other expense	(2,314)	(3,014)
Loss before income taxes	(8,015)	(8,721)
Income taxes (benefit)	(5,000)	(7,421)
Net loss	(3,015)	(1,300)
Statement of Comprehensive Income [Abstract]
Net loss	(3,015)	(1,300)
Other comprehensive income (loss):
Change in foreign currency translation adjustment	(1,868)	652
Comprehensive loss	(4,883)	(648)
Cash flows from operating activities:
Net loss	(3,015)	(1,300)
Adjustments to reconcile net loss to net cash provided by operating activities:
Deferred income taxes	(1,335)	2,497
Others	41,937
Changes in operating assets and liabilities:
Accounts receivable, net	4,329	11,960
Deferred costs and other assets, net	(2,995)
Accounts payable and other liabilities	(21,704)	(37,073)
Deferred revenue	(33)	(4,787)
Net cash provided by operating activities	17,184	4,951
Net cash from investing activities	(10,684)	(10,466)
Net cash from financing activities	(52,586)	(2,112)
Effect of exchange rate changes on cash	(1,094)	430
Net change in cash and cash equivalents	(47,180)	(7,197)
Cash and cash equivalents at beginning of period	142,279	170,343
Cash and cash equivalents at end of period	95,099	$ 163,146
ASC 606 Adjustments | Accounting Standards Update 2014-09
ASSETS
Trade accounts receivable, net	(1,943)
Refundable income taxes	540
Deferred income taxes	(64)
Deferred commissions, net	(18,137)
Others	0
TOTAL ASSETS	(19,604)
Liabilities
Deferred revenue	(232)
Deferred income taxes	(4,761)
Other liabilities	0
Total liabilities	(4,993)
Equity
Retained earnings	(14,611)		$ 12,700
Other equity	0
Total equity	(14,611)
TOTAL LIABILITIES AND EQUITY	(19,604)
Income Statement [Abstract]
Revenues	296
Cost of revenue	0
Gross profit	296
Operating expenses:
Sales and marketing	2,939
Other operating expenses	0
Total operating expenses	2,939
Loss from operations	(2,643)
Total other expense	0
Loss before income taxes	(2,643)
Income taxes (benefit)	(695)
Net loss	(1,948)
Statement of Comprehensive Income [Abstract]
Net loss	(1,948)
Other comprehensive income (loss):
Change in foreign currency translation adjustment	0
Comprehensive loss	(1,948)
Cash flows from operating activities:
Net loss	(1,948)
Adjustments to reconcile net loss to net cash provided by operating activities:
Deferred income taxes	(695)
Others	0
Changes in operating assets and liabilities:
Accounts receivable, net	(256)
Deferred costs and other assets, net	2,939
Accounts payable and other liabilities	0
Deferred revenue	(40)
Net cash provided by operating activities	0
Net cash from investing activities	0
Net cash from financing activities	0
Effect of exchange rate changes on cash	0
Net change in cash and cash equivalents	0
Cash and cash equivalents at beginning of period	0
Cash and cash equivalents at end of period	0
Before ASC topic 606
ASSETS
Trade accounts receivable, net	161,824
Refundable income taxes	12,301
Deferred income taxes	11,424
Deferred commissions, net	0
Others	961,815
TOTAL ASSETS	1,147,364
Liabilities
Deferred revenue	31,389
Deferred income taxes	37,497
Other liabilities	371,033
Total liabilities	439,919
Equity
Retained earnings	623,432
Other equity	84,013
Total equity	707,445
TOTAL LIABILITIES AND EQUITY	1,147,364
Income Statement [Abstract]
Revenues	227,256
Cost of revenue	117,271
Gross profit	109,985
Operating expenses:
Sales and marketing	57,789
Other operating expenses	60,540
Total operating expenses	118,329
Loss from operations	(8,344)
Total other expense	(2,314)
Loss before income taxes	(10,658)
Income taxes (benefit)	(5,695)
Net loss	(4,963)
Statement of Comprehensive Income [Abstract]
Net loss	(4,963)
Other comprehensive income (loss):
Change in foreign currency translation adjustment	(1,868)
Comprehensive loss	(6,831)
Cash flows from operating activities:
Net loss	(4,963)
Adjustments to reconcile net loss to net cash provided by operating activities:
Deferred income taxes	(2,030)
Others	41,937
Changes in operating assets and liabilities:
Accounts receivable, net	4,073
Deferred costs and other assets, net	(56)
Accounts payable and other liabilities	(21,704)
Deferred revenue	(73)
Net cash provided by operating activities	17,184
Net cash from investing activities	(10,684)
Net cash from financing activities	(52,586)
Effect of exchange rate changes on cash	(1,094)
Net change in cash and cash equivalents	(47,180)
Cash and cash equivalents at beginning of period	142,279
Cash and cash equivalents at end of period	$ 95,099