Comprehensive Income (AOCI Rollforward) (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period					$ 17,570,711
Comprehensive Income	49,938,191		34,207,751		100,743,669		89,681,305
Balance at end of period	20,786,416	[1]	15,112,385	[1]	20,786,416	[1]	15,112,385	[1]
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	1,857,184	[1]	2,474,742	[1]	2,458,933	[1]	2,129,957	[1]
Other Comprehensive income before reclassifications	229,115	[1]	(784,992)	[1]	(372,634)	[1]	(440,207)	[1]
Amounts reclassified from accumulated other comprehensive income	0	[1]	0	[1]	0	[1]	0	[1]
Comprehensive Income	229,115	[1]	(784,992)	[1]	(372,634)	[1]	(440,207)	[1]
Balance at end of period	2,086,299	[1]	1,689,750	[1]	2,086,299	[1]	1,689,750	[1]
Unrealized gains(losses) on available-for-sale securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	21,088,438	[1]	19,196,431	[1]	15,111,778	[1]	10,412,246	[1]
Other Comprehensive income before reclassifications	881,260	[1]	(3,991,928)	[1]	8,692,354	[1]	5,763,724	[1]
Amounts reclassified from accumulated other comprehensive income	(3,269,581)	[1]	(1,781,868)	[1]	(5,104,015)	[1]	(2,753,335)	[1]
Comprehensive Income	(2,388,321)	[1]	(5,773,796)	[1]	3,588,339	[1]	3,010,389	[1]
Balance at end of period	$ 18,700,117	[1]	$ 13,422,635	[1]	$ 18,700,117	[1]	$ 13,422,635	[1]

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