Stock-Based Compensation Plans, Stock Option Awards (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock Options [Member]
Share-based Payment Award, Options, Additional Disclosures [Abstract]
Stock options granted (in dollars per share)	$ 10.16	$ 13.67	$ 9.16
Total intrinsic value of stock options exercised	$ 109.8	$ 20.8	$ 5.8
Stock Options and Stock Appreciation Rights [Member]
Shares [Roll Forward]
Outstanding, beginning balance (in shares)	12,352
Granted (in shares)	1,141
Exercised or Settled (in shares)	(5,222)
Forfeited (in shares)	(226)
Expired (in shares)	(17)
Outstanding, ending balance (in shares)	8,028	12,352
Vested (in shares)	6,075
Outstanding Weighted-Average Exercise Price [Abstract]
Outstanding, beginning balance (in dollars per share)	$ 10.93
Granted (in dollars per share)	27.45
Exercised or Settled (in dollars per share)	8.83
Forfeited (in dollars per share)	27.46
Expired (in dollars per share)	31.61
Outstanding, ending balance (in dollars per share)	14.14	$ 10.93
Vested (in dollars per share)	$ 9.93
Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding, weighted average remaining contractual term	5 years 10 months 24 days
Vested, weighted average remaining contractual term	5 years
Outstanding, aggregate intrinsic value of in-the-money options	$ 179.8
Vested, aggregate intrinsic value of in-the-money options	$ 161.4

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of share options (or share units) exercised during the current period.

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