Preparation of Interim Financial Statements and Other Items - Provision for income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Current:
Federal	$ (828)
State	693		$ 1,331
Foreign	682		1,471
Total current income taxes	547		2,802
Deferred:
Federal	6,212		9,451
State	1,074		1,633
Foreign	382		678
Total deferred income taxes	7,668		11,762
Total provision for income taxes	$ 8,215	$ 479	$ 14,564	$ 942