Cash, Cash Equivalents, and Investments

Cash, cash equivalents, and investments consisted of the following (in thousands):



	April 1, 2018		December 31, 2017
Cash	$	101,614	$	97,951
Money market instruments	7,958		8,631
Cash and cash equivalents	109,572		106,582
Treasury bills	138,695		150,371
Corporate bonds	108,313		47,395
Asset-backed securities	75,432		59,203
Municipal bonds	9,153		8,805
Sovereign bonds	6,036		21,579
Agency bonds	—		10,608
Short-term investments	337,629		297,961
Corporate bonds	272,308		296,014
Asset-backed securities	56,246		71,727
Sovereign bonds	16,744		13,147
Agency bonds	5,931		14,890
Treasury bills	3,604		23,459
Municipal bonds	1,348		4,204
Long-term investments	356,181		423,441
	$	803,382	$	827,984

Treasury bills consist of debt securities issued by the U.S. government; corporate bonds consist of debt securities issued by both domestic and foreign companies; asset-backed securities consist of debt securities collateralized by pools of receivables or loans with credit enhancement; municipal bonds consist of debt securities issued by state and local government entities; sovereign bonds consist of direct debt issued by foreign governments; and agency bonds consist of domestic or foreign obligations of government agencies and government sponsored enterprises that have government backing. All securities are denominated in U.S. Dollars.

The following table summarizes the Company’s available-for-sale investments as of April 1, 2018 (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term:
Treasury bills	$	139,159	$	—	$	(464	)	$	138,695
Corporate bonds	108,533		50		(270		)	108,313
Asset-backed securities	75,710		5		(283		)	75,432
Municipal bonds	9,165		—		(12		)	9,153
Sovereign bonds	6,040		1		(5		)	6,036
Long-term:
Corporate bonds	272,345		797		(834		)	272,308
Asset-backed securities	56,573		14		(341		)	56,246
Sovereign bonds	16,779		38		(73		)	16,744
Agency bonds	5,930		1		—			5,931
Treasury bills	3,601		3		—			3,604
Municipal bonds	1,360		—		(12		)	1,348
	$	695,195	$	909	$	(2,294	)	$	693,810

The following table summarizes the Company’s gross unrealized losses and fair values for available-for-sale investments in an unrealized loss position as of April 1, 2018 (in thousands):



	Unrealized Loss Position For:
	Less than 12 Months					12 Months or Greater					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Corporate bonds	$	172,162	$	(812	)	$	23,693	$	(292	)	$	195,855	$	(1,104	)
Treasury bills	96,209		(277		)	42,487		(187		)	138,696		(464		)
Asset-backed securities	112,632		(614		)	2,640		(10		)	115,272		(624		)
Sovereign bonds	3,599		(9		)	8,730		(69		)	12,329		(78		)
Municipal bonds	4,196		(24		)	—		—			4,196		(24		)
Agency bonds	—		—			—		—			—		—
	$	388,798	$	(1,736	)	$	77,550	$	(558	)	$	466,348	$	(2,294	)

As of April 1, 2018, the Company did not recognize any other-than-temporary impairment of these investments. In its evaluation, management considered the type of security, the credit rating of the security, the length of time the security has been in a loss position, the size of the loss position, the Company's intent and ability to hold the security to expected recovery of value, and other meaningful information. The Company does not intend to sell, and is unlikely to be required to sell, any of these available-for-sale investments before their effective maturity or market price recovery.

The Company recorded gross realized gains and gross realized losses on the sale of debt securities totaling $55,000 and $33,000, respectively, during the three-month period ended April 1, 2018 and $88,000 and $23,000, respectively, during the three-month period ended April 2, 2017. These gains and losses are included in "Investment income" on the Consolidated Statement of Operations. Prior to the sale of these securities, unrealized gains and losses for these debt securities, net of tax, are recorded in shareholders’ equity as other comprehensive income (loss).

The following table presents the effective maturity dates of the Company’s available-for-sale investments as of April 1, 2018 (in thousands):



	<1 year		1-2 Years		2-3 Years		3-4 Years		4-5 Years		5-7 Years		Total
Corporate bonds	$	108,313	$	116,223	$	97,412	$	36,342	$	18,961	$	3,370	$	380,621
Treasury bills	138,695		3,604		—		—		—		—		142,299
Asset-backed securities	75,432		35,411		6,923		6,504		2,336		5,072		131,678
Sovereign bonds	6,036		10,995		5,749		—		—		—		22,780
Municipal bonds	9,153		—		1,348		—		—		—		10,501
Agency bonds	—		—		—		—		5,931		—		5,931
	$	337,629	$	166,233	$	111,432	$	42,846	$	27,228	$	8,442	$	693,810