Cash, Cash Equivalents, and Investments

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



	December 31,
	2015		2014
Cash	$	45,951	$	54,917
Money market instruments	6,024		777
Cash and cash equivalents	51,975		55,694
Treasury bills	109,360		—
Asset-backed securities	61,994		1,311
Corporate bonds	54,376		30,889
Euro liquidity fund	47,730		48,235
Sovereign bonds	21,440		—
Agency bonds	978		6,883
Municipal bonds	590		1,237
Supranational bonds	—		1,901
Short-term investments	296,468		90,456
Corporate bonds	176,575		216,294
Treasury bills	44,437		90,412
Asset-backed securities	24,582		62,556
Sovereign bonds	13,503		13,461
Agency bonds	8,180		9,566
Municipal bonds	4,869		6,600
Limited partnership interest (accounted for using cost method)	942		1,956
Long-term investments	273,088		400,845
	$	621,531	$	546,995

The Company’s cash balance included foreign bank balances totaling $39,279,000 and $43,732,000 as of December 31, 2015 and 2014, respectively.

Treasury bills consist of debt securities issued by both the U.S. and foreign governments; asset-backed securities consist of debt securities collateralized by pools of receivables or loans with credit enhancement; corporate bonds consist of debt securities issued by both domestic and foreign companies; the Euro liquidity fund invests in a portfolio of investment-grade bonds; sovereign bonds consist of direct debt issued by foreign governments; agency bonds consist of domestic or foreign obligations of government agencies and government- sponsored enterprises that have government backing; municipal bonds consist of debt securities issued by state and local government entities; and supranational bonds consist of direct debt issued by two or more foreign central governments. 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, 2015 (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term:
Treasury bills	$	109,462	$	2	$	(104	)	$	109,360
Asset-backed securities	62,101		—		$	(107	)	$	61,994
Corporate bonds	54,420		22		(66		)	54,376
Euro liquidity fund	47,667		63		—			47,730
Sovereign bonds	21,466		—		(26		)	21,440
Agency bonds	979		—		(1		)	978
Municipal bonds	590		—		—			590
Long-term:
Corporate bonds	177,748		50		(1,223		)	$	176,575
Treasury bills	44,585		—		(148		)	$	44,437
Asset-backed securities	24,633		2		(53		)	24,582
Sovereign bonds	13,574		—		(71		)	13,503
Agency bonds	8,199		—		(19		)	8,180
Municipal bonds	4,849		20		—			4,869
	$	570,273	$	159	$	(1,818	)	$	568,614

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, 2015 (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	$	162,714	$	(1,092	)	$	24,946	$	(197	)	$	187,660	$	(1,289	)
Treasury bills	127,203		(252		)	—		—			127,203		(252		)
Asset-backed securities	77,165		(154		)	1,783		(6		)	78,948		(160		)
Sovereign bonds	34,943		(97		)	—		—			34,943		(97		)
Agency bonds	9,158		(20		)	—		—			9,158		(20		)
	$	411,183	$	(1,615	)	$	26,729	$	(203	)	$	437,912	$	(1,818	)

As of December 31, 2015, 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 $549,000 in 2015, $843,000 in 2014, and $508,000 in 2013, and gross realized losses on the sale of debt securities totaling $205,000 in 2015, $170,000 in 2014, and $194,000 in 2013. 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 December 31, 2015 (in thousands):



	<1 Year		1-2 Years		2-3 Years		3-4 Years		4-5 Years		5-7 Years		Total
Corporate bonds	$	54,376	$	87,025	$	74,069	$	13,280	$	2,201	$	—	$	230,951
Treasury bills	109,360		19,489		24,948		—		—		—		153,797
Asset-backed securities	61,994		2,491		14,443		3,294		3,960		394		86,576
Euro liquidity fund	47,730		—		—		—		—		—		47,730
Sovereign bonds	21,440		11,026		2,477		—		—		—		34,943
Agency bonds	978		4,894		3,286		—		—		—		9,158
Municipal bonds	590		4,869		—		—		—		—		5,459
	$	296,468	$	129,794	$	119,223	$	16,574	$	6,161	$	394	$	568,614

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. During the fourth quarter of 2015, an amendment to the partnership agreement extended the commitment period by two years to December 31, 2017. The Company does not have the right to withdraw from the partnership prior to this date. As of December 31, 2015, 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 2015. The Company received a cash distribution of $1,014,000 in 2015, which was accounted for as a return of capital. As of December 31, 2015, the carrying value of this investment was $942,000 compared to an estimated fair value of $5,600,000.