Cash Equivalents

The Company had $509,811 and $263,967 of held-to-maturity securities with original maturities of three months or less, primarily consisting of corporate debt securities, classified as cash equivalents at December 31, 2014 and 2013, respectively. The Company's investments in held-to-maturity securities are held at amortized cost, which approximates fair value.

Available-for-Sale Marketable Securities

Investments in available-for-sale securities at December 31 were classified as follows:



	2014		2013
Current	$	—	$	239,388
Non-current	15,414		—
Total available-for-sale securities	$	15,414	$	239,388

The cost, gross unrealized gains, gross unrealized losses and fair value of the Company's available-for-sale securities were as follows:



	December 31, 2014
	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Equity securities	$	15,050	$	364	$	—	$	15,414
Total available-for-sale securities	$	15,050	$	364	$	—	$	15,414



	December 31, 2013
	Cost		Gross Unrealized Gains		Gross Unrealized Losses ⁽¹⁾			Fair Value
Debt securities
Corporate bonds	$	108,300	$	340	$	(69	)	$	108,571
U.S. government debt ⁽²⁾	106,335		60		(79		)	106,316
Asset-backed securities	24,478		34		(11		)	24,501
Total available-for-sale securities	$	239,113	$	434	$	(159	)	$	239,388

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(1)	All unrealized loss positions were held at a loss for less than 12 months.


(2)	U.S. Treasury obligations, U.S. government agency obligations and U.S government agency mortgage-backed securities.

As of December 31, 2014 and December 31, 2013, net unrealized gains on the Company's available-for-sale securities of $233 and $176, respectively, net of income tax expense of $131 and $99, respectively, were recorded in accumulated other comprehensive income. See Note 13 for the fair value hierarchy of the Company's available-for-sale securities.

The proceeds from sales and maturities of available-for-sale securities included in the consolidated statements of cash flows and the gross realized gains and losses included in the consolidated statements of operations are reflected in the table below. The cost of securities sold was determined using the specific identification method. There were no sales or maturities of available-for-sale securities during the year ended December 31, 2012.



	Year Ended December 31,
	2014			2013
Proceeds from sales and maturities of securities	$	342,045		$	7,770
Gross realized gains	1,311			$	20
Gross realized losses	(99		)	$	(39	)