INVESTMENTS AND FAIR VALUE MEASUREMENTS - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Funds held for clients
Total	$ 95,122	$ 72,636
Liabilities:
Contingent purchase consideration	3,880
Total	3,880
Quoted Prices in Active Market (Level 1)
Funds held for clients
Total	69,203	48,500
Liabilities:
Contingent purchase consideration	0
Total	0
Significant Other Observable Inputs (Level 2)
Funds held for clients
Total	25,919	24,136
Liabilities:
Contingent purchase consideration	0
Total	0
Significant Unobservable Inputs (Level 3)
Funds held for clients
Total	0	0
Liabilities:
Contingent purchase consideration	3,880
Total	3,880
Money market funds \| Fair Value, Measurements, Recurring
Cash and cash equivalents
Money market funds	5,204
Money market funds \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Market (Level 1)
Cash and cash equivalents
Money market funds	5,204
Money market funds \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Cash and cash equivalents
Money market funds	0
Money market funds \| Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Cash and cash equivalents
Money market funds	0
Money market funds \| Fair Value, Measurements, Recurring
Funds held for clients
Funds for clients	63,999	48,500
Money market funds \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Market (Level 1)
Funds held for clients
Funds for clients	63,999	48,500
Money market funds \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Funds held for clients
Funds for clients	0	0
Money market funds \| Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Funds held for clients
Funds for clients	0	0
Available-for-sale securities \| Fair Value, Measurements, Recurring
Funds held for clients
Funds for clients	25,919	24,136
Available-for-sale securities \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Market (Level 1)
Funds held for clients
Funds for clients	0	0
Available-for-sale securities \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Funds held for clients
Funds for clients	25,919	24,136
Available-for-sale securities \| Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Funds held for clients
Funds for clients	$ 0	$ 0

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Funds Held For Clients

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Fair value portion of other liabilities.

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