Investments (Tables)

12 Months Ended

Dec. 31, 2016

Amortized Cost and Fair Value of Available for Sale Investments

The amortized cost and fair values of available-for-sale investments are as follows at December 31, 2016 and December 26, 2015 (in thousands):    

			Gross		Gross
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
December 31, 2016
Money market investments	$	12,395	$	—	$	—	$	12,395
Asset-backed securities		4,027		3		19		4,011
Corporate bonds and direct obligations of government agencies		70,069		150		239		69,980
U.S. Treasury obligations		23,037		2		6		23,033
Total	$	109,528	$	155	$	264	$	109,419
December 26, 2015
Money market investments	$	7,594	$	—	$	—	$	7,594
Asset-backed securities		4,523		1		58		4,466
Corporate bonds and direct obligations of government agencies		76,839		190		270		76,759
U.S. Treasury obligations		19,273		5		13		19,265
Total	$	108,229	$	196	$	341	$	108,084

Schedule of Unrealized Loss on Available for Sale Investments

For those available-for-sale investments with unrealized losses at December 31, 2016 and December 26, 2015, the following table summarizes the duration of the unrealized loss (in thousands):

	Less than 12 months				12 months or longer				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
December 31, 2016
Asset-backed securities	$	1,363	$	6	$	2,314	$	13	$	3,677	$	19
Corporate bonds and direct obligations of government agencies		28,809		195		1,367		44		30,176		239
U.S. Treasury obligations		12,734		6		—		—		12,734		6
Total	$	42,906	$	207	$	3,681	$	57	$	46,587	$	264
December 26, 2015
Asset-backed securities	$	4,422	$	58	$	—	$	—	$	4,422	$	58
Corporate bonds and direct obligations of government agencies		39,276		217		562		53		39,838		270
U.S. Treasury obligations		15,093		13		—		—		15,093		13
Total	$	58,791	$	288	$	562	$	53	$	59,353	$	341