Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2018	Jun. 30, 2018
Accumulated Other Comprehensive Income
Period Start Balance	$ 236,369	$ 236,369
Period End Balance		128,047
Amounts reclassified from other comprehensive income	0	0
Unrealized Gain/(Loss) on Marketable Securities
Accumulated Other Comprehensive Income
Period Start Balance	(32)	(32)
Other comprehensive loss		26
Period End Balance		(6)
Foreign Currency Items
Accumulated Other Comprehensive Income
Period Start Balance	2,596	2,596
Period End Balance		2,596
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income
Period Start Balance	$ 2,564	2,564
Other comprehensive loss		26
Period End Balance		$ 2,590