Earnings (Loss) per Share - Reconciliation of Weighted-Average Common Shares Outstanding (Details) - shares shares in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Determination of shares:
Weighted average common shares outstanding - basic (in shares)	126.8	116.0	121.3	116.1
Assumed conversion of convertible preferred shares (in shares)	0.8		0.6
Assumed conversion of convertible debt (in shares)	7.9		4.0
Weighted-average common shares outstanding - Diluted (in shares)	126.8	117.7	121.3	118.2
Anti-dilutive securities, stock options (in shares)	3.0	2.0	1.9	1.9
Stock options
Determination of shares:
Assumed conversion of dilutive employee stock-based awards and restricted stock (in shares)	1.5	1.6	1.8	1.9
Restricted stock
Determination of shares:
Assumed conversion of dilutive employee stock-based awards and restricted stock (in shares)	0.2	0.1	0.3	0.2

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the if-converted method.

+ References

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible preferred stock using the if-converted method.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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