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Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Statement of Comprehensive Income [Abstract]      
Changes in defined benefit pension plans, tax amount $ 4,152 $ (2,455) $ 21,139
Changes in fair value of derivative, tax amount $ 0 $ 142 $ 148