Income Taxes (Income Tax Reconciliation) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Domestic statutory rate at 35%	$ 19,851,000	$ 28,828,000	$ 21,766,000
Increase (reduction) from:
Jurisdictional rate differences	719,000	(1,863,000)	(1,936,000)
Valuation allowance	(267,000)	308,000	1,731,000
Stock based compensation	(205,000)	(778,000)	275,000
U.S. state taxes	3,917,000	2,463,000	1,295,000
Domestic production deduction	0	(1,039,000)	(618,000)
R&D credit	(531,000)	(500,000)	(329,000)
GILTI	673,000	0	0
Other, net	219,000	397,000	(40,000)
Provision for income taxes before tax reform	24,376,000	27,816,000	22,144,000
Tax Reform:
Rate change of deferreds	1,200,000	(3,334,000)	0
Transition tax on deemed repatriation	(4,531,000)	13,104,000	0
Other	0	466,000	0
Impact of tax reform	(3,331,000)	10,236,000	0
Total income taxes	$ 21,045,000	$ 38,052,000	$ 22,144,000
Effective tax rate	26.00%	34.00%
Effective tax rate	22.00%	46.00%	36.00%