Investments

The following tables summarize our short-term investments (dollars in thousands):



		As of September 30, 2015
	Maturity (in years)	Amortized cost		Gross unrealized gains		Gross unrealized losses		Estimated fair value
Corporate debt securities	1 year or less	$	25,381	$	1	$	—	$	25,382
Commercial paper	1 year or less	2,749		1		—		2,750
		$	28,130	$	2	$	—	$	28,132



		As of December 31, 2014
	Maturity (in years)	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
Corporate debt securities	1 year or less	$	21,208	$	3	$	(1	)	$	21,210
Commercial paper	1 year or less	1,500		—		—			1,500
		$	22,708	$	3	$	(1	)	$	22,710

Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At September 30, 2015, the Company did not have any securities in material unrealized loss positions. The Company reviews its investments to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee, and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. The Company does not intend to sell any investments prior to recovery of their amortized cost basis for any investments in an unrealized loss position.