SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 93,767	$ 89,912	$ 85,682	$ 83,225	$ 79,344	$ 75,575	$ 72,483	$ 69,098	$ 66,489	$ 63,676	$ 63,183	$ 60,041	$ 352,586	$ 296,500	$ 253,388
Gross profit	59,174	56,962	54,083	52,395	49,685	49,996	46,037	44,055
Loss from operations	(28,780)	(24,238)	(21,987)	(15,983)	(13,730)	(18,247)	(4,462)	(5,457)	$ (3,685)	$ (1,703)	$ (379)	$ (901)	(90,988)	(41,896)	(6,669)
Net loss	$ (28,131)	$ (23,771)	$ (21,482)	$ (15,355)	$ (13,262)	$ (88,520)	$ (546)	$ (2,169)					$ (88,739)	$ (104,497)	$ (4,751)
Net income (loss) per share:
Basic and diluted (in dollars per share)	$ (0.29)	$ (0.25)	$ (0.23)	$ (0.16)	$ (0.14)	$ (0.96)	$ (0.01)	$ (0.02)					$ (0.94)	$ (1.14)	$ (0.05)

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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