Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2015

Fair Value of Financial Assets and Liabilities Measured on Recurring Basis

The following table sets forth the fair value of our financial assets and liabilities, allocated into Level 1, Level 2 and Level 3, that was measured on a recurring basis (in thousands):

	March 31, 2015
	Level 1		Level 2		Level 3		Total
Financial Assets:
Money market funds	$	55,862	$	—	$	—	$	55,862
Corporate notes and commercial paper		—		254,939		—		254,939
U.S. government agency securities		—		131,708		—		131,708
Total financial assets	$	55,862	$	386,647	$	—	$	442,509

	December 31, 2014
	Level 1		Level 2		Level 3		Total
Financial Assets:
Money market funds	$	24,915	$	—	$	—	$	24,915
Corporate notes and commercial paper		—		226,047		—		226,047
U.S. government agency securities		—		120,169		—		120,169
Total financial assets	$	24,915	$	346,216	$	—	$	371,131