Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2015

Fair Value Disclosures [Abstract]

Assets Measured or Disclosed at Fair Value on Recurring Basis

Assets measured or disclosed at fair value on a recurring basis as of June 30, 2015 are summarized below:

	Fair Value Measurements Using
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Cash and cash equivalents	$	76,248	$	—	$	—	$	76,248
Certificates of deposit		—		19,721		—		19,721
U.S. Government debt securities		—		38,542		—		38,542
Corporate debt securities		—		18,278		—		18,278
	$	76,248	$	76,541	$	—	$	152,789

Assets measured or disclosed at fair value on a recurring basis as of December 31, 2014 are summarized below:

	Fair Value Measurements Using
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Cash and cash equivalents	$	32,780	$	—	$	—	$	32,780
Certificates of deposit		—		13,429		—		13,429
U.S. Government debt securities		—		38,385		—		38,385
Commercial paper		—		2,499		—		2,499
Corporate debt securities		—		21,825		—		21,825
	$	32,780	$	76,138	$	—	$	108,918