Note 6 - Unearned Revenue (Details Textual) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020
Revenue, Remaining Performance Obligation, Amount	$ 3,452,021	$ 3,325,737	$ 3,535,639
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Revenue, Remaining Performance Obligation, Amount	$ 2,500,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period (Month)	12 months

Period in which remaining performance obligation is expected to be recognized as revenue, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130556-203045

Name:	us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant