Fair Value Measurements Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2018

Fair Value Disclosures [Abstract]

Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block]

The following tables summarize the levels of fair value measurements of our financial assets:

	Fair Value Measurements
	(in thousands)
	June 30, 2018		Level 1		Level 2		Level 3
Money market funds	$	299,691	$	299,691	$	—	$	—
Municipal bonds	7,207		—		7,207		—
Total	$	306,898	$	299,691	$	7,207	$	—

	Fair Value Measurements
	(in thousands)
	December 31, 2017		Level 1		Level 2		Level 3
Money market funds	$	360,746	$	360,746	$	—	$	—
Municipal bonds	1,960		—		1,960		—
Total	$	362,706	$	360,746	$	1,960	$	—