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Stock-Based Compensation (Stock Units Converted To Common Stock) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Payment Arrangement [Abstract]      
Total intrinsic value of vested stock units converted to common stock $ 8.0 $ 12.1 $ 22.7