4. Financial Instruments

The Company elected to invest a portion of its cash assets in conservative, income earning, liquid investments effective September 2015. Cash equivalents and investments, all of which are classified as available-for-sale securities, consisted of the following:


	December 31, 2016								December 31, 2015
	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	$	5,966	$	—	$	—	$	5,966
U.S. Treasury securities		57,846		—		(404)		57,442		104,537		1		(725)		103,813
U.S. agency securities		56,261		—		(147)		56,114		79,491		—		(638)		78,853
Municipal securities		17,478		—		(174)		17,304		18,974		2		(56)		18,920
Total	$	142,362	$	—	$	(725)	$	141,637	$	208,968	$	3	$	(1,419)	$	207,552

Classified as:
Cash equivalents							$	10,777							$	5,966
Short-term investments								130,860								201,586
Total							$	141,637							$	207,552

The Company invests in U.S. Treasuries, U.S. agency and high quality municipal bonds which mature at par and are all paying their coupons on schedule. Thus, the Company has determined there is currently no other than temporary impairment of our investments, and will continue to recognize unrealized losses and gains in other comprehensive income. For the year ended December 31, 2016, the Company had $0.2 million in realized gains and immaterial realized losses for a total net realized gain of $0.2 million as a result of the sale of investments. There was no sale of investments for the year ended December 31, 2015.

As of December 31, 2016, the Company has 27 investments in an unrealized loss position in its portfolio. Available-for-sale debt securities that were in a continuous loss position but were not deemed to be other than temporarily impaired were immaterial as of December 31, 2016. The Company earned interest income of $1.5 million during the year ended December 31, 2016. The following table summarizes the Company’s portfolio of available-for-sale securities by contractual maturity as of December 31, 2016:


	December 31, 2016
	Amortized Cost		Fair Value
	(in thousands)
Less than one year	$	48,265	$	48,212
Greater than one year but less than five years		83,320		82,648
Total	$	131,585	$	130,860