Comprehensive Income (AOCI Rollforward) (Details) (USD $)	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$ 17,570,711
Comprehensive Income	50,805,478		55,473,554
Balance at end of period	22,945,622	[1]	21,671,173	[1]
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	2,458,933	[1]	2,129,957	[1]
Other Comprehensive income before reclassifications	(601,749)	[1]	344,785	[1]
Amounts reclassified from accumulated other comprehensive income	0	[1]	0	[1]
Comprehensive Income	(601,749)	[1]	344,785	[1]
Balance at end of period	1,857,184	[1]	2,474,742	[1]
Unrealized gains(losses) on available-for-sale securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	15,111,778	[1]	10,412,246	[1]
Other Comprehensive income before reclassifications	7,811,095	[1]	9,755,652	[1]
Amounts reclassified from accumulated other comprehensive income	(1,834,435)	[1]	(971,467)	[1]
Comprehensive Income	5,976,660	[1]	8,784,185	[1]
Balance at end of period	$ 21,088,438	[1]	$ 19,196,431	[1]

[1] All amounts are shown net of tax. Amounts in parentheses indicate debits.