Quarterly report pursuant to Section 13 or 15(d)

CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical)

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CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Current assets    
Allowance for doubtful accounts $ 31,693 $ 29,634