Investments (Tables)

3 Months Ended

Mar. 31, 2018

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 March 31, 2018 and December 30, 2017 (in thousands):

			Gross		Gross
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
March 31, 2018
Money market investments	$	26,096	$	—	$	—	$	26,096
Asset-backed securities		1,878		—		8		1,870
Corporate bonds and direct obligations of government agencies		83,764		25		1,130		82,659
Total	$	111,738	$	25	$	1,138	$	110,625
December 30, 2017
Money market investments	$	27,895	$	—	$	—	$	27,895
Asset-backed securities		2,805		—		5		2,800
Corporate bonds and direct obligations of government agencies		80,442		117		335		80,224
Total	$	111,142	$	117	$	340	$	110,919

Schedule of Unrealized Loss on Available-for-Sale Investments

For those available-for-sale investments with unrealized losses at March 31, 2018 and December 30, 2017, 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
March 31, 2018
Asset-backed securities	$	1,870	$	8	$	—	$	—	$	1,870	$	8
Corporate bonds and direct obligations of government agencies		65,717		953		9,931		177		75,648		1,130
Total	$	67,587	$	961	$	9,931	$	177	$	77,518	$	1,138
December 30, 2017
Asset-backed securities	$	1,864	$	4	$	632	$	1	$	2,496	$	5
Corporate bonds and direct obligations of government agencies		41,322		220		14,016		115		55,338		335
Total	$	43,186	$	224	$	14,648	$	116	$	57,834	$	340