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, 2015								December 31, 2014
	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	$	5,966	$	—	$	—	$	5,966	$	—	$	—	$	—	$	—
U.S. Treasury securities		104,537		1		(725)		103,813		—		—		—		—
U.S. agency securities		79,491		—		(638)		78,853		—		—		—		—
Municipal securities		18,974		2		(56)		18,920
Total	$	208,968	$	3	$	(1,419)	$	207,552	$	—	$	—	$	—	$	—

Classified as:
Cash equivalents							$	5,966							$	—
Short-term investments								201,586								—
Total							$	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. As of December 31, 2015, the Company has 73 investments in an unrealized loss position in its portfolio. The Company earned interest income of $0.3 million during the year ended December 31, 2015. The following table summarizes the Company’s portfolio of available-for-sale securities by contractual maturity as of December 31, 2015:


	December 31, 2015
	Amortized Cost		Fair Value
	(in thousands)
Less than one year	$	55,128	$	55,010
Greater than one year but less than five years		153,840		152,542
Total	$	208,968	$	207,552