Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2013

Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]

Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table presents our fair value hierarchy for our assets and liabilities measured at fair value on a recurring basis at December 31, 2013 (in thousands):

	Level 1		Level 2		Level 3		Total
Cash and cash equivalents:
Cash	$	69,333	$	—	$	—	$	69,333
Money market funds	35,248		—		—		35,248
Commercial paper	—		261,722		—		261,722
Short-term investments:
Commercial paper	—		124,319		—		124,319
Corporate notes and bonds	—		143,932		—		143,932
Long-term investments:
Corporate notes and bonds	—		255,356		—		255,356
Total	$	104,581	$	785,329	$	—	$	889,910

The following table presents our fair value hierarchy for our assets and liabilities measured at fair value on a recurring basis at December 31, 2012 (in thousands): 

	Level 1		Level 2		Level 3		Total
Cash and cash equivalents:
Cash	$	47,478	$	—	$	—	$	47,478
Money market funds	35,429		—		—		35,429
Commercial paper	—		36,082		—		36,082
Short-term investments:
Commercial paper	—		36,753		—		36,753
Corporate notes and bonds	—		157,948		—		157,948
U.S. government agency securities	—		1,001		—		1,001
Total	$	82,907	$	231,784	$	—	$	314,691