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Shareholders' Equity (Shares Repurchased Under Share Repurchase Program) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Class of Stock [Line Items]
Aggregate purchase price	$ 11.2	$ 33.5	$ 73.4	$ 26.6
Stock Repurchase Program Board Authorized Repurchases [Member]
Class of Stock [Line Items]
Shares repurchased (in shares)	0.3		1.6		1.3	2.1
Aggregate purchase price	$ 11.2		$ 73.4		$ 44.7	$ 100.0
Average purchase price per share (in dollars per share)	$ 39.54		$ 47.30		$ 35.51	$ 47.58
Remaining amount available for share repurchase	$ 219.0				$ 219.0

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Amount remaining of a stock repurchase plan authorized.

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Total cost of shares repurchased divided by the total number of shares repurchased.

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Number of shares that have been repurchased during the period and are being held in treasury.

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Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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