REVENUE RECOGNITION - Financial Statement Impact of Adoption (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Apr. 01, 2018	Mar. 31, 2018
ASSETS:
Accounts receivable and unbilled costs	$ 247,690		$ 247,690		$ 214,633	$ 213,438
Inventories and deferred costs	28,909		28,909			34,774
Prepaid expenses and other current assets	27,001		27,001		38,128	33,502
Other assets	19,298		19,298		17,614	12,866
LIABILITIES:
Deferred revenue and customer deposits	260,926		260,926		271,698	301,925
Deferred tax liability	129,284		129,284		159,462	151,563
Long-term deferred revenue and customer deposits	84,881		84,881		90,157	91,409
STOCKHOLDERS' EQUITY:
Retained earnings	338,107		338,107		430,642	$ 396,493
Income Statement [Abstract]
Total revenue	246,008	$ 268,944	674,916	$ 751,563
Total cost of revenue	69,584	64,509	195,591	205,314
Sales and marketing	74,024	77,270	224,207	239,897
Income tax benefit	(1,602)	(54,531)	(23,479)	(69,093)
Net income (loss)	$ (3,603)	$ 89,685	$ (92,535)	$ 62,995
Basic net loss per share (in USD per share)	$ (0.05)	$ 1.03	$ (1.17)	$ 0.71
Diluted net loss per share (in USD per share)	$ (0.05)	$ 1.02	$ (1.17)	$ 0.70
Balance without Adoption of Topic 606
ASSETS:
Accounts receivable and unbilled costs	$ 237,738		$ 237,738
Inventories and deferred costs	29,130		29,130
Prepaid expenses and other current assets	23,434		23,434
Other assets	13,851		13,851
LIABILITIES:
Deferred revenue and customer deposits	278,939		278,939
Deferred tax liability	123,333		123,333
Long-term deferred revenue and customer deposits	98,239		98,239
STOCKHOLDERS' EQUITY:
Retained earnings	311,636		311,636
Income Statement [Abstract]
Total revenue	245,318		664,666
Total cost of revenue	69,609		195,370
Sales and marketing	74,607		223,804
Income tax benefit	(2,001)		(25,427)
Net income (loss)	$ (4,502)		$ (100,213)
Basic net loss per share (in USD per share)	$ (0.06)		$ (1.27)
Diluted net loss per share (in USD per share)	$ (0.06)		$ (1.27)
Accounting Standards Update 2014-09 | Effect of Change Higher (Lower)
ASSETS:
Accounts receivable and unbilled costs	$ 9,952		$ 9,952		1,195
Inventories and deferred costs	(221)		(221)
Prepaid expenses and other current assets	3,567		3,567		4,626
Other assets	5,447		5,447		4,748
LIABILITIES:
Deferred revenue and customer deposits	(18,013)		(18,013)		(30,227)
Deferred tax liability	5,951		5,951		7,899
Long-term deferred revenue and customer deposits	(13,358)		(13,358)		(1,252)
STOCKHOLDERS' EQUITY:
Retained earnings	26,471		26,471		$ 34,149
Income Statement [Abstract]
Total revenue	690		10,250
Total cost of revenue	(25)		221
Sales and marketing	(583)		403
Income tax benefit	399		1,948
Net income (loss)	$ 899		$ 7,678
Basic net loss per share (in USD per share)	$ 0.01		$ 0.10
Diluted net loss per share (in USD per share)	$ 0.01		$ 0.10