CUSTOMER FUNDS - Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value (Details) - Customer funds - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	$ 56,984	$ 46,661
Less than 12 Months, Gross Unrealized Losses	(22)	(7)
Greater than 12 months, Fair Value	0	0
Greater than 12 months, Gross Unrealized Losses	0	0
Total, Fair Value	56,984	46,661
Total, Gross Unrealized Losses	(22)	(7)
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	56,984	34,818
Less than 12 Months, Gross Unrealized Losses	(22)	(3)
Greater than 12 months, Fair Value	0	0
Greater than 12 months, Gross Unrealized Losses	0	0
Total, Fair Value	56,984	34,818
Total, Gross Unrealized Losses	$ (22)	(3)
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value		11,843
Less than 12 Months, Gross Unrealized Losses		(4)
Greater than 12 months, Fair Value		0
Greater than 12 months, Gross Unrealized Losses		0
Total, Fair Value		11,843
Total, Gross Unrealized Losses		$ (4)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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