Taxes on Income - Components of Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 3,764	$ (636)	$ 2,150
Foreign	7,512	3,585	5,600
State	3,351	175	528
Subtotal	14,627	3,124	8,278
Deferred:
Federal	(8,706)	2,158	218
Foreign	(1,099)	475	1,382
State	183	352	(673)
State	(9,622)	2,985	927
Total tax provision	$ 5,005	$ 6,109	$ 9,205