Comprehensive Income (AOCI Rollforward) (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period					$ 17,570,711
Comprehensive Income	56,833,393		44,881,549		157,577,062		134,562,853
Balance at end of period	22,098,848	[1]	18,116,852	[1]	22,098,848	[1]	18,116,852	[1]
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	2,086,299	[1]	1,689,750	[1]	2,458,933	[1]	2,129,957	[1]
Other Comprehensive income before reclassifications	273,097	[1]	275,648	[1]	(99,537)	[1]	(164,559)	[1]
Amounts reclassified from accumulated other comprehensive income	0	[1]	0	[1]	0	[1]	0	[1]
Comprehensive Income	273,097	[1]	275,648	[1]	(99,537)	[1]	(164,559)	[1]
Balance at end of period	2,359,396	[1]	1,965,398	[1]	2,359,396	[1]	1,965,398	[1]
Unrealized gains(losses) on available-for-sale securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	18,700,117	[1]	13,422,635	[1]	15,111,778	[1]	10,412,246	[1]
Other Comprehensive income before reclassifications	5,240,576	[1]	4,901,805	[1]	13,932,930	[1]	10,665,529	[1]
Amounts reclassified from accumulated other comprehensive income	(4,201,241)	[1]	(2,172,986)	[1]	(9,305,256)	[1]	(4,926,321)	[1]
Comprehensive Income	1,039,335	[1]	2,728,819	[1]	4,627,674	[1]	5,739,208	[1]
Balance at end of period	$ 19,739,452	[1]	$ 16,151,454	[1]	$ 19,739,452	[1]	$ 16,151,454	[1]

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