Cash and Cash Equivalents and Investments in Marketable Securities

Our investment portfolio at March 31, 2014 consisted of cash, cash equivalents and investments in marketable securities.

We currently invest in marketable debt securities with the maximum maturity or put date of any individual issue generally not greater than one year from the date of purchase, which are usually held until maturity. All of these instruments are classified as available-for-sale. As a result, they are reported at fair value using quoted market prices. Interest income is recorded as earned. Unrealized gains and losses, net of related income taxes, are reported as a component of accumulated other comprehensive income. Upon sale or maturity, realized gains on our marketable debt securities are recognized as interest income. These gains are computed based on the specific identification of the underlying cost of the securities, net of unrealized gains and losses previously reported in other comprehensive income. Unrealized gains and losses on our available-for-sale securities are due to changes in market prices and are considered temporary.

The following is a summary of our marketable securities:



	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value (Net Carrying Amount)
	(In thousands)
March 31, 2014
Certificates of deposit	$	64,703	$	20	$	—		$	64,723
Commercial paper	72,568		20		—			72,588
Corporate debt securities	136,056		15		(64		)	136,007
State and political subdivisions debt securities	442,167		66		(33		)	442,200
Total marketable securities	$	715,494	$	121	$	(97	)	$	715,518

December 31, 2013
Certificates of deposit	$	74,802	$	21	$	(1	)	$	74,822
Commercial paper	78,216		28		—			78,244
Corporate debt securities	96,889		6		(44		)	96,851
State and political subdivisions debt securities	475,235		49		(41		)	475,243
Total marketable securities	$	725,142	$	104	$	(86	)	$	725,160

Interest income recognized on our marketable securities was $0.6 million and $0.5 million for the three months ended March 31, 2014 and 2013, respectively.