Comprehensive Income (AOCI Rollforward) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period			$ 21,975,363	[1]
Comprehensive Income	68,956,915	56,833,393	209,792,103		157,577,062
Balance at end of period	14,137,766	22,098,848	14,137,766		22,098,848
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	2,175,183	2,086,299	2,507,922		2,458,933
Other Comprehensive (loss) income before reclassifications	(269,392)	273,097	(602,131)		(99,537)
Amounts reclassified from accumulated other comprehensive income	0	0	0		0
Comprehensive Income	(269,392)	273,097	(602,131)		(99,537)
Balance at end of period	1,905,791	2,359,396	1,905,791		2,359,396
Unrealized gains on available-for-sale securities:
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	15,342,551	18,700,117	19,467,441		15,111,778
Other Comprehensive (loss) income before reclassifications	(1,604,338)	5,240,576	1,788,502		13,932,930
Amounts reclassified from accumulated other comprehensive income	(1,506,238)	(4,201,241)	(9,023,968)		(9,305,256)
Comprehensive Income	(3,110,576)	1,039,335	(7,235,466)		4,627,674
Balance at end of period	$ 12,231,975	$ 19,739,452	$ 12,231,975		$ 19,739,452

[1] Note: The condensed consolidated balance sheet at December 31, 2013 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements.