Short-Term Investments (Tables)

12 Months Ended

Sep. 29, 2018

Cash, Cash Equivalents, and Short-term Investments [Abstract]

Schedule of cash, cash equivalents and short-term investments

Cash, cash equivalents and short-term investments consist of the following (in thousands):

	Fiscal 2018 year-end
	Cost Basis		Unrealized Gains		Unrealized Losses		Fair Value
Cash and cash equivalents	$	310,495	$	—	$	—	$	310,495
Short-term investments:
Available-for-sale securities:
U.S. Treasury and agency obligations	120		—		—		120
Total short-term investments	$	120	$	—	$	—	$	120

	Fiscal 2017 year-end
	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash and cash equivalents	$	443,066	$	—	$	—		$	443,066
Short-term investments:
Available-for-sale securities:
U.S. Treasury and agency obligations	21,074		13		—			21,087
Corporate notes and obligations	11,390		34		(1		)	11,423
Total short-term investments	$	32,464	$	47	$	(1	)	$	32,510

Schedule of amortized cost and estimated fair value of available-for-sale investments in debt securities

The amortized cost and estimated fair value of available-for-sale investments in debt securities as of September 29, 2018 and September 30, 2017 classified as short-term investments on our consolidated balance sheets, were as follows (in thousands):

	Fiscal year-end
	2018				2017
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Investments in available-for-sale debt securities due in less than one year	$	120	$	120	$	30,214	$	30,251
Investments in available-for-sale debt securities due in one to five years (1)	$	—	$	—	$	2,250	$	2,259

(1) Classified as short-term investments because these securities are highly liquid and can be sold at any time.