Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2019

Fair Value Measurements [Abstract]

Fair Value, by Balance Sheet Grouping [Table Text Block]

	Assets and Liabilities at Fair Value as of September 30, 2019
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash and cash equivalents	$	170,203	$	—	$	—	$	170,203
Short-term investments	126,101		—		—		126,101
Total cash and cash equivalents and investments	$	296,304	$	—	$	—	$	296,304

	Assets and Liabilities at Fair Value as of December 31, 2018
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash and cash equivalents	$	80,386	$	—	$	—	$	80,386
Short-term investments	73,974		5,692		—		79,666
Total cash and cash equivalents and investments	$	154,360	$	5,692	$	—	$	160,052