Cash and Investments (Tables)

12 Months Ended

Dec. 31, 2016

Investments Debt And Equity Securities [Abstract]

Cash, Cash Equivalents and Available-for-Sale Investments

The following table presents cash, cash equivalents, and available-for-sale investments as of the following dates (in thousands):

	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Market Value
Cash	$	43,604	$	—	$	—		$	43,604
Cash equivalents:
Money market funds		959		—		—			959
Commercial paper and corporate debt securities		2,499		—		—			2,499
Marketable securities:
U.S. Treasury securities		5,667		—		—			5,667
U.S. Government agency securities		11,412		—		(7	)		11,405
Certificates of deposits		23,000		19		—			23,019
Commercial paper		22,402		—		—			22,402
Corporate debt securities		14,194		—		(6	)		14,188
Municipal securities		756		—		(1	)		755
Asset-backed securities		5,466		—		(3	)		5,463
Total cash, cash equivalents, and marketable    securities	$	129,959	$	19	$	(17	)	$	129,961
	December 26, 2015
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Market Value
Cash	$	32,996	$	—	$	—		$	32,996
Cash equivalents:
Money market funds		590		—		—			590
Commercial paper and corporate debt securities		4,568		—		—			4,568
Marketable securities:
U.S. Treasury securities		4,411		—		(10	)		4,401
U.S. Government agency securities		20,193		1		(29	)		20,165
Commercial paper		1,884		—		—			1,884
Corporate debt securities		14,759		—		(23	)		14,736
Municipal securities		3,747		1		(3	)		3,745
Total cash, cash equivalents, and marketable    securities	$	83,148	$	2	$	(65	)	$	83,085