Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2017

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 measured at fair value on a recurring basis at June 30, 2017 (in thousands): 

	Level 1		Level 2		Total
Cash equivalents:
Money market funds	$	217,219	$	—	$	217,219
Certificates of deposit	—		1,000		1,000
U.S. government agency securities	—		607,548		607,548
Short-term investments:
Commercial paper	—		68,075		68,075
Corporate notes and bonds	—		387,571		387,571
Certificates of deposit	—		17,505		17,505
U.S. government agency securities	—		23,354		23,354
Marketable equity securities	22,214		—		22,214
Long-term investments:
Corporate notes and bonds	—		268,076		268,076
Certificates of deposit	—		18,884		18,884
U.S. government agency securities	—		32,835		32,835
Total	$	239,433	$	1,424,848	$	1,664,281

The following table presents our fair value hierarchy for our assets measured at fair value on a recurring basis at December 31, 2016 (in thousands): 

	Level 1		Level 2		Total
Cash equivalents:
Money market funds	$	165,627	$	—	$	165,627
Short-term investments:
Commercial paper	—		56,839		56,839
Corporate notes and bonds	—		388,429		388,429
Certificates of deposit	—		35,355		35,355
U.S. government agency securities	—		17,501		17,501
Long-term investments:
Corporate notes and bonds	—		238,125		238,125
U.S. government agency securities	—		24,533		24,533
Total	$	165,627	$	760,782	$	926,409