4. Financial Instruments

The Company has invested a portion of its cash assets in conservative, income earning, and liquid investments. Cash equivalents and investments, all of which are classified as available-for-sale securities, consisted of the following:


	June 30, 2017								December 31, 2016
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized (Loss)		Estimated Fair Value		Amortized Cost		Gross Unrealized Gain		Gross Unrealized (Loss)		Estimated Fair Value
	(in thousands)
Money market deposits	$	—	$	—	$	—	$	—	$	10,777	$	—	$	—	$	10,777
U.S. Treasury securities		35,387		—		(303)		35,084		57,846		—		(404)		57,442
U.S. agency securities		47,130		—		(151)		46,979		56,261		—		(147)		56,114
Municipal securities		12,934		6		(15)		12,925		17,478		—		(174)		17,304
Total	$	95,451	$	6	$	(469)	$	94,988	$	142,362	$	—	$	(725)	$	141,637

Classified as:
Cash equivalents							$	—							$	10,777
Short-term investments								94,988								130,860
Total							$	94,988							$	141,637

The Company invests in U.S. Treasuries, U.S. agency and high quality municipal bonds which mature at par value and are all paying their coupons on schedule. The Company has therefore concluded there is currently no other than temporary impairment of its investments and will continue to recognize unrealized gains and losses in other comprehensive income (loss). During the three and six months ended June 30, 2017, the Company had immaterial realized gains and losses. The Company uses the specific investment identification method to calculate realized gains and losses and amounts reclassified out of other comprehensive income to net income. As of June 30, 2017, the Company has 19 investments in an unrealized loss position in its portfolio. The Company earned interest income of $0.2 million and $0.5 million during the three and six months ended June 30, 2017, respectively. The following table summarizes the Company’s portfolio of available-for-sale securities by contractual maturity as of June 30, 2017:


	June 30, 2017
	Amortized Cost		Fair Value
	(in thousands)
Less than one year	$	31,831	$	31,776
Greater than one year but less than five years		63,620		63,212
Total	$	95,451	$	94,988