Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2019

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 March 31, 2019
	Total		Level 1		Level 2		Level 3
Cash, Cash Equivalents	$	290,885	$	290,885	$	—	$	—
Marketable Securities
Bonds and bond funds	$	154,407	$	—	$	154,407	$	—
Commercial paper		98,990		—		98,990		—
		253,397		—		253,397		—
Total Assets Measured at Fair Value	$	544,282	$	290,885	$	253,397	$	—

	Fair Value Measurements as of December 31, 2018
	Total		Level 1		Level 2		Level 3
Cash, Cash Equivalents	$	328,384	$	328,384	$	—	$	—
Marketable Securities
Bonds and bond funds	$	229,783	$	—	$	229,783	$	—
Commercial paper		131,162		—		131,162		—
		360,945		—		360,945		—
Total Assets Measured at Fair Value	$	689,329	$	328,384	$	360,945	$	—