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Revenues Revenue from Contracts with Customers (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Revenue from Contract with Customer [Abstract]      
Contract with Customer, Liability, Revenue Recognized $ 9,300 $ 6,800 $ 5,000
Contract with Customer, Liability $ 13,666 $ 14,276