Fair Value (Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation) (Details) - Fair Value, Inputs, Level 3 [Member] - Fair Value, Measurements, Recurring [Member] - Auction Rate Securities [Member] $ in Millions	12 Months Ended
	Sep. 29, 2017 USD ($)
Fair Value, Assets [Roll Forward]
Auction rate securities beginning balance	$ 2.3
Changes in fair value included in earnings	(2.3)
Auction rate securities ending balance	$ 0.0