Taxes on Income, Reconciliation of Liability for Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the beginning and ending amount of the liability for unrecognized tax benefits [Roll Forward]
Balance at beginning of year	$ 2,019	$ 1,958	$ 1,171
Additions based on tax positions related to the current year	403	187	339
Additions for tax positions of prior years	273	867	785
Reductions for tax positions of prior years	(908)	(441)	(337)
Settlements	0	(552)	0
Balance at end of year	1,787	2,019	1,958
Income tax penalties and interest recognized	120	88	216
Accrued liabilities for payment of interest and penalties	$ 675	$ 554	$ 522