Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Measurements

Schedule of assets measured at fair value on a recurring basis

Assets measured at fair value on a recurring basis are summarized below (in thousands):

	Fair Value Measurements as of September 30, 2017
	Total		Level 1		Level 2		Level 3
Marketable Securities
Bonds and bond funds	$	414,578	$	—	$	414,578	$	—
Commercial paper		154,502		—		154,502		—
	$	569,080	$	—	$	569,080	$	—
Cash, Cash Equivalents and Restricted Cash		106,363		106,363		—		—
Total Assets Measured at Fair Value	$	675,443	$	106,363	$	569,080	$	—

	Fair Value Measurements as of December 31, 2016
	Total		Level 1		Level 2		Level 3
Marketable Securities
Bonds and bond funds	$	409,885	$	—	$	409,885	$	—
Commercial paper		13		—		13		—
	$	409,898	$	—	$	409,898	$	—
Cash, Cash Equivalents and Restricted Cash		155,009		155,009		—		—
Total Assets Measured at Fair Value	$	564,907	$	155,009	$	409,898	$	—