Annual report pursuant to Section 13 and 15(d)

NATURE OF OPERATIONS AND ACCOUNTING POLICIES - Schedule of Allowance for Doubtful Accounts (Details)

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NATURE OF OPERATIONS AND ACCOUNTING POLICIES - Schedule of Allowance for Doubtful Accounts (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance at beginning of period $ 34,967 $ 21,575 $ 12,650
Write-offs 0 (4,196) 0
Balance at end of period 37,869 34,967 21,575
Allowance for Doubtful Accounts      
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance at beginning of period 1,196 1,219 2,103
Additional allowances charged to expense 82 144 441
Recovery of previously reserved accounts (127) (82) (1,086)
Write-offs (760) (68) (474)
Foreign currency adjustments (130) (17) 235
Balance at end of period $ 261 $ 1,196 $ 1,219