Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2019

Fair Value Measurements

Schedule of assets measured at fair value on a recurring basis

	Fair Value Measurements as of September 30, 2019
	Total		Level 1		Level 2		Level 3
Cash and cash equivalents	$	307,909	$	307,909	$	—	$	—
Marketable securities
Bonds and bond funds	$	207,538	$	—	$	207,538	$	—
Commercial paper		56,059		—		56,059		—
		263,597		—		263,597		—
Total assets measured at fair value	$	571,506	$	307,909	$	263,597	$	—

	Fair Value Measurements as of December 31, 2018
	Total		Level 1		Level 2		Level 3
Cash and 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	$	—