Preparation of Interim Financial Statements and Other Items - Provision for income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Current:
Federal	$ 617		$ 828
State	398		638
Foreign	551		789
Total current income taxes	1,566		2,255
Deferred:
Federal	2,477		3,239
State	431		559
Foreign	223		296
Total deferred income taxes	3,131		4,094
Total provision for income taxes	$ 4,697	$ 309	$ 6,349	$ 463