Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2016

Fair Value of Financial Instruments [Abstract]

Financial Assets Measured at Fair Value on a Recurring Basis

Financial assets measured at fair value on a recurring basis were as follows (in thousands):

	Fair Value Measurements at March 31, 2016
				Quoted Prices in Active Markets for Identical Assets			Significant Other Observable Inputs			Significant Unobservable Inputs
	Total			Level 1			Level 2			Level 3
Assets:
Money market funds		$	64,820		$	64,820		$	–		$	–
U.S. Treasury securities			9,311			–			9,311			–
Government-sponsored enterprises			33,670			–			33,670			–
Corporate debt securities			139,008			–			139,008			–
Total assets measured at fair value^(a)		$	246,809		$	64,820		$	181,989		$	–

(a) Total assets measured at fair value at March 31, 2016 includes approximately $94.3 million reported in cash and cash equivalents on the balance sheet.

	Fair Value Measurements at December 31, 2015
				Quoted Prices in Active Markets for Identical Assets			Significant Other Observable Inputs			Significant Unobservable Inputs
	Total			Level 1			Level 2			Level 3
Assets:
Money market funds		$	62,353		$	62,353		$	–		$	–
U.S. Treasury securities			9,349			–			9,349			–
Government-sponsored enterprises			41,202			–			41,202			–
Corporate debt securities			137,928			–			137,928			–
Total assets measured at fair value^(a)		$	250,832		$	62,353		$	188,479		$	–

(a) Total assets measured at fair value at December 31, 2015 includes approximately $108.0 million reported in cash and cash equivalents on the balance sheet.