5. Cash Equivalents and Marketable Debt Securities

As of March 31, 2018, all of the Company’s marketable debt securities are classified as available-for-sale and are scheduled to mature within 3.5 years. At March 31, 2018, the detail of the Company’s cash equivalents and marketable debt securities is as follows (in thousands):

	March 31, 2018
	(unaudited)
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Corporate debt securities	$	86,952	$	1	$	(222	)	$	86,731
Government sponsored securities		12,508		—		(15	)		12,493
Foreign government bonds		5,936		—		(5	)		5,931
Commercial paper		5,441		—		(3	)		5,438
Current portion		110,837		1		(245	)		110,593
Noncurrent:
Corporate debt securities		12,642		—		(248	)		12,394
Government sponsored securities		2,759		—		(62	)		2,697
Noncurrent portion		15,401		-		(310	)		15,091
Total	$	126,238	$	1	$	(555	)	$	125,684

At December 31, 2017, the detail of the Company’s cash equivalents and marketable debt securities is as follows (in thousands):

	December 31, 2017
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Corporate debt securities	$	82,188	$	5	$	(84	)	$	82,109
Government sponsored securities		19,261		—		(28	)		19,233
Foreign government bonds		6,441		—		(5	)		6,436
Current portion		107,890		5		(117	)		107,778
Noncurrent:
Corporate debt securities		27,109		—		(226	)		26,883
Government sponsored securities		2,760		—		(43	)		2,717
Noncurrent portion		29,869		—		(269	)		29,600
Total	$	137,759	$	5	$	(386	)	$	137,378

Included in foreign government bonds is $3.5 million of cash equivalents at December 31, 2017.

Available-for-sale investments that had been in an unrealized loss position for more and less than 12 months at March 31, 2018 and December 31, 2017 are as follows (in thousands):

	March 31, 2018
	(unaudited)
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	73,914	$	(208	)	$	23,211	$	(262	)
Government sponsored securities		1,999		(7	)		13,191		(70	)
Foreign government bonds		4,533		(2	)		1,397		(3	)
Commercial paper		5,438		(3	)		—		—
Total	$	85,884	$	(220	)	$	37,799	$	(335	)

	December 31, 2017
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	67,522	$	(104	)	$	35,918	$	(206	)
Government sponsored securities		9,744		(20	)		12,205		(51	)
Foreign government bonds		1,542		—			1,396		(5	)
Total	$	78,808	$	(124	)	$	49,519	$	(262	)

The Company evaluated its securities for other-than-temporary impairment and concluded that the decline in value was primarily caused by current economic and market conditions. The Company does not intend to sell the investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases. Therefore, the Company did not have any other-than-temporary impairment loss during the three months ended March 31, 2018. At March 31, 2018, 63 of the securities and bonds are in an unrealized loss position.

The Company recorded realized gains and losses on sales or maturities of available-for-sale securities as follows (in thousands):

	Three Months Ended March 31,
	(unaudited)
	2018		2017
Gross realized gains	$	2	$	2
Gross realized losses		—		(5	)
Net realized gains	$	2	$	(3	)