Shareholders' Equity and Earnings Per Common Share -Common Shares Repurchased (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2020	Mar. 31, 2020
Shareholders' Equity and Earnings Per Common Share
Authorized value of shares for repurchase			$ 500.0
Repurchase and retired common shares	1.4	2.9
Repurchase and retired common shares, Value	$ 38.4	$ 79.6
Average purchase price	$ 26.64	$ 27.82

Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

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