Cash and Cash Equivalents and Investments in Marketable Securities

Our investment portfolio at December 31, 2013 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)
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



	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value (Net Carrying Amount)
	(In thousands)
December 31, 2012
Certificates of deposit	$	82,791	$	14	$	(6	)	$	82,799
Commercial paper	45,737		17		—			45,754
Corporate debt securities	49,587		2		(30		)	49,559
State and political subdivisions debt securities	457,615		26		(51		)	457,590
Total marketable securities	$	635,730	$	59	$	(87	)	$	635,702

Interest income recognized on our marketable securities was $2.1 million and $1.1 million for the years ended December 31, 2013 and 2012, respectively.