Fair Value Measurements

3 Months Ended

Mar. 31, 2016

Fair Value Measurements [Abstract]

Fair Value Measurements

Note 4 – Fair Value Measurements

The following table represents the Company’s fair value hierarchy for its financial assets and liabilities measured at fair value (in thousands):

	Fair Value at March 31, 2016						Fair Value at December 31, 2015
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Assets
Money market funds	$	49,321	$	—	$	—	$	14,950	$	—	$	—
U.S. Treasury securities		—		21,791		—		—		—		—
Debt securities of U.S. government agencies		—		35,871		—		—		—		—
Government-backed security		—		39,500		—		—		20,000		—
Asset-backed securities		—		62,557		—		—		28,924		—
Corporate debt securities		—		217,645		—		—		137,213		—
Total assets	$	49,321	$	377,364	$	—	$	14,950	$	186,137	$	—
Liabilities
Convertible notes payable	$	—	$	317,021	$	—	$	—	$	—	$	—

Fixed-income investments categorized as Level 2 are valued at the custodian bank by a third-party pricing vendor’s valuation models that use verifiable observable market data, e.g., interest rates and yield curves observable at commonly quoted intervals and credit spreads, bids provided by brokers or dealers or quoted prices of securities with similar characteristics. Pricing of the Company’s Notes (See Note 7) has been estimated using other observable inputs, including the price of the Company’s common stock, implied volatility, interest rates and credit spreads among others. Over time, the Company expects a market for the Notes to develop. At that time, the Company intends to use trade data as the principal basis for measuring fair value.

During the three months ended March 31, 2016, the Company did not have any transfers between levels.

The amounts in the Company’s consolidated balance sheet for accounts receivable and accounts payable approximate fair value due to their short-term nature. Based on borrowing rates available to the Company, the fair value of capital lease and notes payable approximates their carrying value. The Company’s milestone payment due to Wyeth (See Note 11) approximates its fair value at March 31, 2016, as the liability has been calculated based on an anticipated future payment date discounted at borrowing rates available to the Company.