Stockholders' Equity (Changes in Shares of Common Stock Outstanding) (Details) - shares shares in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity [Line Items]
Beginning balance	282.1	288.4	292.8
Stock plans activity	1.1	0.9	1.1
Share repurchases	(4.8)	(7.2)	(5.5)
Ending balance	278.4	282.1	288.4

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Number, after forfeiture, of shares or units issued under share-based payment arrangement. Excludes shares or units issued under employee stock ownership plan (ESOP).

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

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