5. Cash, Cash Equivalents and Available for Sale Securities

The Company considers all highly liquid investments purchased with original maturities at the date of purchase of 90 days or less to be cash equivalents. Cash and cash equivalents included cash of $4.7 million and $6.8 million at December 31, 2014 and 2013, respectively. Cash and cash equivalents at December 31, 2014 and December 31, 2013 also included investments of $35.1 million and $203.8 million, respectively, in U.S. Treasury securities with original maturities of less than 90 days and investments in money market funds that invest in U.S. Treasury Securities.

At December 31, 2014, the Company held available for sale securities with a fair value totaling $423.7 million. These available for sale securities consisted of U.S. Treasury securities and had maturities less than one year. The Company evaluates securities with unrealized losses, if any, to determine whether such losses are other than temporary. The Company has determined that there were no other than temporary declines in fair values of its investments as of December 31, 2014. The Company classifies these securities as available for sale, however, the Company does not currently intend to sell its investments and it is more likely than not that the Company will recover the carrying value of these investments. Unrealized gains (losses) are reported as a component of accumulated other comprehensive loss in stockholders’ equity. The unrealized loss, net of tax, was $0.1 million as of December 31, 2014. As of December 31, 2013, the Company did not hold any available for sale securities.

Available for sale securities, including carrying value and estimated fair values, are summarized as follows:

	As of December 31, 2014
	Cost		Fair Value		Carrying Value		Unrealized Loss
U.S. Treasury securities—maturities < 1 year	$	423,859	$	423,746	$	423,746	$	(113	)
U.S. Treasury securities—maturities > 1 year	$	—	$	—	$	—	$	—

Total	$	423,859	$	423,746	$	423,746	$	(113	)