FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Dec. 29, 2017	Sep. 29, 2017
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	$ 18.5	$ 59.8
DRTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	8.0	8.0
APTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	6.0
GPTC Securities [Member]
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	4.5	4.4
Fair Value, Measurements, Recurring
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	18.5	59.8
Derivative liabilities:	(0.4)
Total liabilities measured at fair value	(0.4)
Fair Value, Measurements, Recurring \| Original CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		47.4
Fair Value, Measurements, Recurring \| DRTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	8.0	8.0
Fair Value, Measurements, Recurring \| APTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	6.0
Fair Value, Measurements, Recurring \| GPTC Securities [Member]
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	4.5	4.4
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Instruments
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0.0	0.0
Derivative liabilities:	0.0
Total liabilities measured at fair value	0.0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Instruments \| Original CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		0.0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Instruments \| DRTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0	0.0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Instruments \| APTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Instruments \| GPTC Securities [Member]
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0	0.0
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	18.5	12.4
Derivative liabilities:	(0.4)
Total liabilities measured at fair value	(0.4)
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs \| Original CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		0.0
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs \| DRTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	8.0	8.0
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs \| APTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	6.0
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs \| GPTC Securities [Member]
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	4.5	4.4
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0.0	47.4
Derivative liabilities:	0.0
Total liabilities measured at fair value	0.0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs \| Original CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		47.4
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs \| DRTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0	0.0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs \| APTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs \| GPTC Securities [Member]
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	$ 0.0	$ 0.0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
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-URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226008-175313

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Fair value of financial and nonfinancial obligations.

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