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Summary of Significant Accounting Policies Per Common Share Information (Details) - shares
shares in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Earnings Per Share [Abstract]      
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements 6.8 7.3 8.1
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 0.1 0.5 0.1