RESTATEMENT OF PREVIOUSLY ISSUED FINANCIAL STATEMENTS - Impact of Restatement Adjustments on Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and restricted cash	$ 63,134		$ 119,419	$ 97,378		$ 54,326
Accounts Receivable	205,817		166,941
Inventory	106,376		97,071
Federal income taxes receivable	10,906		2,987
Goodwill	308,880		261,767
Total assets	912,957		868,131
Accounts Payable	91,385		64,849
Other current liabilities	40,583		34,729
Total liabilities	551,617		506,995
Cumulative Translation Adjustment	(17,538)		(18,013)
Retained earnings	201,626		186,078
Total equity	361,340	$ 354,109	361,136	$ 334,166	$ 368,456	$ 354,932
Total liabilities and equity	$ 912,957		868,131
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and restricted cash			117,444
Accounts Receivable			163,429
Inventory			97,071
Federal income taxes receivable			5,632
Goodwill			248,339
Total assets			851,861
Accounts Payable			75,744
Other current liabilities			20,834
Total liabilities			503,995
Cumulative Translation Adjustment			(21,842)
Retained earnings			176,637
Total equity			347,866
Total liabilities and equity			851,861
Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and restricted cash			1,975
Accounts Receivable			3,512
Inventory			0
Federal income taxes receivable			(2,645)
Goodwill			13,428
Total assets			16,270
Accounts Payable			(10,895)
Other current liabilities			13,895
Total liabilities			3,000
Cumulative Translation Adjustment			3,829
Retained earnings			9,441
Total equity			13,270
Total liabilities and equity			$ 16,270