Presentation of Financial Information - Earning Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
Dec. 31, 2017	Jan. 01, 2017
BASIC
Net income	$ 47.9	$ 19.5
Weighted-average common shares outstanding (in shares)	116.9	114.0
Basic earnings (loss) per share (USD per share)	$ 0.41	$ 0.17
DILUTED
Net income	$ 47.9	$ 19.5
Weighted-average common shares outstanding (in shares)	116.9	114.0
Dilutive effect of stock awards	2.0	2.3
Weighted-average common shares outstanding on a diluted basis (in shares)	118.9	116.3
Diluted earnings per share (USD per share)	$ 0.40	$ 0.17
Stock awards excluded in computation of diluted EPS	1.2	0.3

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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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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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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