Consolidated Statements of Comprehensive Loss (Parenthetical) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 30, 2019	Mar. 31, 2018	Mar. 30, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Changes in unrealized holding gains and losses on available-for-sale securities. tax	$ 0.0	$ 0.0		$ 0.2
Changes in pension plans, tax	0.0	0.0		0.6
Changes in value of hedged interest rate caps, tax	$ 0.3	$ 0.3	$ 0.8	$ (4.6)

Amount, after reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income for defined benefit plan, attributable to parent.

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Amount of tax expense (benefit), after reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

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