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SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (Details) - Allowance for doubtful accounts - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Movement in valuation and qualifying accounts      
Balance at Beginning of Period $ 4,771 $ 5,105 $ 7,715
Charged to Costs and Expenses 1,273 935 1,056
Deductions (1,070) (1,269) (3,666)
Balance at End of Period $ 4,974 $ 4,771 $ 5,105