Income Taxes Components of income tax expense/ (benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Federal:
Current									$ (82)	$ 0
Deferred									0	0
Total federal provision									(82)	0
State:
Current									1	18
Deferred									0	0
Total state provision									1	18
Foreign:
Current									53	164
Deferred									0	0
Total foreign provision									53	164
Total income tax expense	$ (53)	$ 2	$ 29	$ (6)	$ 102	$ 23	$ 51	$ 6	$ (28)	$ 182