Cash, Cash Equivalents, and Investments

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



	December 31,
	2016		2015
Cash	$	77,307	$	45,951
Money market instruments	2,334		6,024
Cash and cash equivalents	79,641		51,975
Corporate bonds	141,188		54,376
Asset-backed securities	69,614		61,994
Treasury bills	67,175		109,360
Euro liquidity fund	46,499		47,730
Sovereign bonds	7,298		21,440
Municipal bonds	6,517		590
Agency bonds	2,903		978
Short-term investments	341,194		296,468
Corporate bonds	169,952		176,575
Treasury bills	92,280		44,437
Asset-backed securities	26,946		24,582
Sovereign bonds	23,585		13,503
Agency bonds	10,339		8,180
Municipal bonds	1,233		4,869
Limited partnership interest (accounted for using cost method)	—		942
Long-term investments	324,335		273,088
	$	745,170	$	621,531

The Company’s cash balance included foreign bank balances totaling $68,076,000 and $39,279,000 as of December 31, 2016 and 2015, respectively.

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; treasury bills consist of debt securities issued by the U.S. government; the Euro liquidity fund invests in a portfolio of investment-grade bonds; sovereign bonds consist of direct debt issued by foreign governments; municipal bonds consist of debt securities issued by state and local government entities; and agency bonds consist of domestic or foreign obligations of government agencies and government- sponsored enterprises that have government backing. The Euro liquidity fund is denominated in Euros, and the remaining securities are denominated in U.S. Dollars.

The following table summarizes the Company’s available-for-sale investments as of December 31, 2016 (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term:
Corporate bonds	$	141,216	$	37	$	(65	)	$	141,188
Asset-backed securities	69,623		18		(27		)	69,614
Treasury bills	67,201		21		(47		)	67,175
Euro liquidity fund	46,173		326		—			46,499
Sovereign bonds	7,313		—		(15		)	7,298
Municipal bonds	6,517		2		(2		)	6,517
Agency bonds	2,900		3		—			2,903
Long-term:
Corporate bonds	169,911		406		(365		)	169,952
Treasury bills	92,392		40		(152		)	92,280
Asset-backed securities	26,968		25		(47		)	26,946
Sovereign bonds	23,704		6		(125		)	23,585
Agency bonds	10,310		29		—			10,339
Municipal bonds	1,236		—		(3		)	1,233
	$	665,464	$	913	$	(848	)	$	665,529

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 December 31, 2016 (in thousands):



	Unrealized Loss Position For Less than 12 Months					Unrealized Loss Position For Greater than 12 Months					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Corporate bonds	$	117,853	$	(400	)	$	14,931	$	(30	)	$	132,784	$	(430	)
Treasury bills	99,358		(199		)	—		—			99,358		(199		)
Asset-backed securities	45,429		(70		)	5,998		(4		)	51,427		(74		)
Sovereign bonds	27,687		(140		)	—		—			27,687		(140		)
Municipal bonds	4,028		(5		)	—		—			4,028		(5		)
	$	294,355	$	(814	)	$	20,929	$	(34	)	$	315,284	$	(848	)

As of December 31, 2016, 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, our 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 its effective maturity or market price recovery.

The Company recorded gross realized gains on the sale of debt securities totaling $292,000 in 2016, $549,000 in 2015, and $843,000 in 2014, and gross realized losses on the sale of debt securities totaling $101,000 in 2016, $205,000 in 2015, and $170,000 in 2014. 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 summarizes the effective maturity dates of the Company’s available-for-sale investments as of December 31, 2016 (in thousands):



	<1 Year		1-2 Years		2-3 Years		3-4 Years		4-5 Years		Total
Corporate bonds	$	141,188	$	84,007	$	77,975	$	2,211	$	5,759	$	311,140
Treasury bills	67,175		92,280		—		—		—		159,455
Asset-backed securities	69,614		8,957		7,372		10,530		87		96,560
Euro liquidity fund	46,499		—		—		—		—		46,499
Sovereign bonds	7,298		19,007		4,578		—		—		30,883
Agency bonds	2,903		7,614		2,725		—		—		13,242
Municipal bonds	6,517		1,233		—		—		—		7,750
	$	341,194	$	213,098	$	92,650	$	12,741	$	5,846	$	665,529

The Company is a Limited Partner in Venrock Associates III, L.P. (Venrock), a venture capital fund. The Company has committed to a total investment in the limited partnership of up to $20,500,000 with an expiration date of December 31, 2017. The Company does not have the right to withdraw from the partnership prior to this date. As of December 31, 2016, the Company contributed $19,886,000 to the partnership. The remaining commitment of $614,000 can be called by Venrock at any time before December 31, 2017. Contributions and distributions are at the discretion of Venrock’s management. No contributions were made in 2016. The Company received cash distributions totaling $2,257,000 in 2016, of which $942,000 was accounted for as a return of capital, reducing the carrying value of this investment to zero, with the remaining $1,315,000 recorded as investment income.