INCOME TAX - Change in Valuation Allowance (Details) - USD ($) $ in Thousands	7 Months Ended	12 Months Ended
	Dec. 31, 2016	May 31, 2016	May 31, 2015
Movement in Deferred Tax Valuation Allowance [Roll Forward]
Valuation allowance, beginning of period	$ (15,119)	$ (3,823)	$ (7,199)
Valuation allowance, end of period	(16,611)	(15,119)	(3,823)
Utilization of foreign net operating loss carryforwards
Movement in Deferred Tax Valuation Allowance [Roll Forward]
Valuation allowance, change	(1,504)	(4,474)
Other
Movement in Deferred Tax Valuation Allowance [Roll Forward]
Valuation allowance, change		98	(11)
Allowance for domestic net unrealized capital loss
Movement in Deferred Tax Valuation Allowance [Roll Forward]
Valuation allowance, change		(1,526)
Release of allowance of domestic net unrealized capital loss
Movement in Deferred Tax Valuation Allowance [Roll Forward]
Valuation allowance, change	$ 12	1,746
Foreign Tax Authority \| Utilization of foreign net operating loss carryforwards
Movement in Deferred Tax Valuation Allowance [Roll Forward]
Valuation allowance, change			$ 3,387
Foreign Tax Authority \| Allowance for foreign income tax credit carryforward
Movement in Deferred Tax Valuation Allowance [Roll Forward]
Valuation allowance, change		(7,140)
Heartland Payment Systems, Inc \| Utilization of foreign net operating loss carryforwards
Movement in Deferred Tax Valuation Allowance [Roll Forward]
Valuation allowance, change		$ (4,474)