Cash and Cash Equivalents and Available for Sale Securities

The Company considers all highly liquid investments purchased with original maturities at the date of purchase of three months or less to be cash equivalents. At September 30, 2017 and December 31, 2016, the Company had cash and cash equivalents of $166.7 million and $541.8 million, respectively, which consisted of cash of $152.0 million and $485.7 million, and money market funds with original maturities of less than three months of $14.7 million and $56.1 million at September 30, 2017 and December 31, 2016, respectively.

At September 30, 2017, the Company held available for sale securities with a fair value totaling $42.2 million. These available for sale securities consist of corporate debt securities and asset backed securities. At September 30, 2017, all of the $42.2 million of available for sale securities are due within one year. The Company evaluates securities with unrealized losses to determine whether such losses are other than temporary.

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



	As of September 30, 2017
	Amortized Cost		Fair Value		Unrealized Gain
	(in thousands)
Asset backed securities	8,192		8,192		—
Corporate debt securities	33,973		33,976		3
Total	$	42,165	$	42,168	$	3

The Company does not intend to sell its corporate debt securities and it is not more likely than not that the Company will be required to sell its corporate debt securities before recovery of their amortized cost basis, which may be maturity.

Restricted Cash

The Company had restricted cash of $5.0 million at September 30, 2017 and December 31, 2016, respectively, which included $3.7 million and $1.0 million reserved for an outstanding letter of credit associated with foreign taxes and the Company’s lease for the office space in Parsippany, New Jersey, respectively, at both September 30, 2017 and December 31, 2016, respectively. These funds are invested in certificates of deposit. The letter of credit for the Company’s lease for the office space in Parsippany, New Jersey permits draws by the landlord to cure defaults by the Company. In addition, as a result of the acquisition of Targanta Therapeutics Corporation (Targanta) in 2009, the Company had restricted cash of $0.1 million at both September 30, 2017 and December 31, 2016, in the form of a guaranteed investment certificate collateralizing an available credit facility. The Company also had restricted cash of $0.2 million at September 30, 2017 and December 31, 2016, respectively, related to certain foreign tender requirements.