Condensed Consolidated Statements Of Cash Flows (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Condensed Consolidated Statements Of Cash Flows [Abstract]
Net cash flows provided by operating activities	$ 11,858,738	$ 4,349,701
Cash flows from investing activities:
Purchases of property, plant and equipment	(2,732,673)	(2,301,908)
Purchases of long-term marketable securities	(179,166)	(191,942)
Proceeds from sale of long-term marketable securities	153,257	181,404
Proceeds from U.K. government grant	0	484,499
Net cash flows used in investing activities	(2,758,582)	(1,827,947)
Cash flows from financing activities:
Dividends paid	(1,858,608)	(1,854,928)
Proceeds from the issuance of common stock	78,000	0
Excess tax benefits from the exercise of stock options	13,130	0
Net cash flows used in financing activities	(1,767,478)	(1,854,928)
Effect of exchange rate changes on cash and cash equivalents	502,219	283,992
Net increase in cash and cash equivalents	7,834,897	950,818
Cash and cash equivalents at beginning of period	69,887,839	70,020,838
Cash and cash equivalents at end of period	77,722,736	70,971,656
Supplemental information:
Income tax payments	996,964	213,288
Interest payments	56,010	77,041
Non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 691,902	$ 1,356,068