3. Cash Equivalents and Marketable Securities

The following tables summarize the estimated fair value of our cash equivalents and marketable securities and the gross unrealized gains and losses (in thousands):

	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Cash equivalents:
Money market funds	$	4,584	$	—	$	—		$	4,584
Reverse repurchase agreements		39,250		—		—			39,250
Total cash equivalents		43,834		—		—			43,834
Marketable securities:
US government and agency securities		15,758		—		(4	)		15,754
Total marketable securities	$	15,758	$	—	$	(4	)	$	15,754

	December 31, 2015
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Cash equivalents:
Money market funds	$	3,988	$	—	$	—		$	3,988
Reverse repurchase agreements		16,250		—		—			16,250
Total cash equivalents		20,238		—		—			20,238
Marketable securities:
US government and agency securities		3,769		—		(1	)		3,768
Total marketable securities	$	3,769	$	—	$	(1	)	$	3,768

The reverse repurchase agreements are settled in cash nightly, and as such are classified as cash equivalents. All of the cash equivalents and marketable securities held as of December 31, 2016 and 2015 had maturities of less than one year.

As of December 31, 2016 and 2015, the Company held nine and five debt securities, respectively, that were in an unrealized loss position for less than one year. The aggregate fair value of debt securities in an unrealized loss position as of December 31, 2016 and 2015 were $15.8 million and $2.5 million, respectively, with no individual securities in a significant unrealized loss position. The Company evaluated its securities for other-than-temporary impairment and considered the decline in market value for the securities to be primarily attributable to current economic and market conditions and would not be required to sell the securities before recovery of the amortized cost basis. Based on this analysis, these marketable securities were not considered to be other-than-temporarily impaired as of December 31, 2016 and 2015.