ACQUISITIONS - Narrative (Details) $ in Thousands		1 Months Ended			12 Months Ended
	Apr. 01, 2018 USD ($)	Jul. 31, 2018 USD ($) shares	Apr. 30, 2018 USD ($)	Jan. 31, 2018 USD ($) business	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Business Acquisition [Line Items]
Face amount	$ 450
Stock issued upon acquisition					$ 555
Intangibles						$ 40,323
Remaining amortization period					8 years 6 months	8 years 109 days
Transaction costs incurred						$ 1,347
Contingent consideration	489
Other income						489
Pay Systems
Business Acquisition [Line Items]
Payments to acquire shares				$ 13,935
Principal amount				$ 1,572
Stated interest rate				2.00%
Purchase price				$ 15,507
Intangibles				$ 7,240
Tele Payroll Pay Systems And Savers Admin
Business Acquisition [Line Items]
Number of businesses acquired | business				2
USA Payroll
Business Acquisition [Line Items]
Payments to acquire shares		$ 18,561
Stated interest rate		3.00%
Purchase price		$ 27,504
Face amount		$ 3,263
Stock issued during period for acquisition (in Shares) | shares		225,089
Stock issued upon acquisition		$ 3,600
Intangibles		$ 17,643
Customer Relationships
Business Acquisition [Line Items]
Intangibles	$ 10,444					$ 33,554
Remaining amortization period	8 years				8 years 10 months 24 days	9 years
Customer Relationships | Minimum
Business Acquisition [Line Items]
Discount rate						13.00%
Customer Relationships | Maximum
Business Acquisition [Line Items]
Discount rate						33.00%
Developed Technology
Business Acquisition [Line Items]
Intangibles						$ 2,100
Remaining amortization period					6 years	6 years
Trade Names
Business Acquisition [Line Items]
Intangibles						$ 2,330
Royalty rate						1.00%
Remaining amortization period					3 years	13 years 4 months
Noncompete Agreements
Business Acquisition [Line Items]
Intangibles						$ 330
Remaining amortization period					5 years 2 months 12 days	5 years 73 days
Evolution Payroll
Business Acquisition [Line Items]
Costs capitalized to complete acquisition	$ 40
Evolution Payroll | Evolution Payroll
Business Acquisition [Line Items]
Purchase price			$ 10,450
Evolution Payroll | Customer Relationships | Evolution Payroll
Business Acquisition [Line Items]
Payments to acquire shares			10,000
Evolution Payroll | Legal Fees
Business Acquisition [Line Items]
Costs capitalized to complete acquisition	30
Evolution Payroll | Accounting Fees
Business Acquisition [Line Items]
Costs capitalized to complete acquisition	$ 10
Evolution Payroll Note | Evolution Payroll | Customer Relationships | Evolution Payroll
Business Acquisition [Line Items]
Principal amount			$ 450
Stated interest rate			2.00%
Second Restated Credit Agreement | Evolution Payroll | Customer Relationships | Evolution Payroll
Business Acquisition [Line Items]
Face amount			$ 10,000