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Shareholders' Equity (Share Repurchased Under Share Repurchase Program) (Details) - USD ($) $ / shares in Units, shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Feb. 12, 2021
Class of Stock [Line Items]
Aggregate purchase price	$ 382,300,000	$ 44,700,000	$ 100,000,000.0
Stock Repurchase Program Board Authorized Repurchases [Member]
Class of Stock [Line Items]
Shares repurchased (in shares)	7.2	1.3	2.1
Aggregate purchase price	$ 382,300,000	$ 44,700,000	$ 100,000,000.0
Average purchase price per share (in dollars per share)	$ 52.76	$ 35.51	$ 47.58
Remaining amount available for share repurchase	$ 197,800,000
Stock Repurchase Program Board Authorized Repurchases [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Increase in share repurchase authorization				$ 1,000,000,000

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Amount of 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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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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