7. FINANCIAL INSTRUMENTS - Other Information (Details) - USD ($)	3 Months Ended
Jun. 30, 2019	Mar. 31, 2019
Other information
Maximum maturity period of investment portfolio	3 years
Deferred tax liability related to unrecognized gains and losses on short-term and long-term investments	$ 16,000	$ 2,000

Amount of deferred tax liability attributable to taxable temporary differences from investments (excludes investments in subsidiaries and equity method investments).

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant