Marketable Securities

The following is a summary of marketable securities designated as available-for-sale as of December 31, 2014 and 2013:



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
December 31, 2014
Corporate bonds	$	99,592	$	1	$	(119	)	$	99,474
Municipal bonds	18,146		1		(10		)	18,137
Commercial paper	9,196		—		—			9,196
Certificates of deposit	498		—		—			498
Total marketable securities	$	127,432	$	2	$	(129	)	$	127,305
December 31, 2013
Corporate bonds	$	37,399	$	1	$	(29	)	$	37,371
Municipal bonds	10,820		2		(3		)	10,819
Certificates of deposit	498		—		—			498
Total marketable securities	$	48,717	$	3	$	(32	)	$	48,688

All marketable securities are classified as current regardless of contractual maturity dates because we consider such investments to represent cash available for current operations.

As of December 31, 2014 and 2013, we did not consider any of our marketable securities to be other-than-temporarily impaired. When evaluating our investments for other-than-temporary impairment, we review factors such as the length of time and extent to which fair value has been below its cost basis, the financial condition of the issuer, our ability and intent to hold the security, and whether it is more likely than not that we will be required to sell the investment before recovery of its cost basis.

The following is a summary of amortized cost and estimated fair value of marketable securities as of December 31, 2014 and 2013, by maturity:



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
December 31, 2014
Due in one year or less	$	127,029	$	2	$	(129	)	$	126,902
Due after one year	403		—		—			403
Total marketable securities	$	127,432	$	2	$	(129	)	$	127,305
December 31, 2013
Due in one year or less	$	47,398	$	3	$	(32	)	$	47,369
Due after one year	1,319		—		—			1,319
Total marketable securities	$	48,717	$	3	$	(32	)	$	48,688