Income Taxes (Income Tax Reconciliation) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal statutory percentage rate	35.00%	35.00%	35.00%
Domestic statutory rate at 35%	$ 21,766,000	$ 23,403,000	$ 21,212,000
Increase (reduction) from:
Jurisdictional rate differences	(1,936,000)	(2,192,000)	(2,119,000)
Valuation allowance	1,731,000	797,000	353,000
Stock based compensation	275,000	257,000	199,000
U.S. state taxes	1,295,000	1,942,000	1,649,000
Domestic production deduction	(618,000)	(518,000)	(1,321,000)
R&D credit	(329,000)	(475,000)	(614,000)
Other, net	(40,000)	444,000	95,000
Total income taxes	$ 22,144,000	$ 23,658,000	$ 19,454,000
Effective tax percentage rate	36.00%	35.00%	32.00%