Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Measurements [Abstract]

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

	Assets and Liabilities at Fair Value as of March 31, 2019
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash and cash equivalents	$	45,778	$	—	$	—	$	45,778
Short-term investments	87,367				—		87,367
Total cash and cash equivalents and investments	$	133,145	$	—	$	—	$	133,145

	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