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Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Statement [Abstract]      
Unrealized loss on investment, taxes $ 247 $ 43 $ 0
Adjustment to postretirement benefit plans, taxes $ (324) $ 22 $ 0