Comprehensive Income (AOCI Rollforward) (Details) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	[1]			$ 11,313,015
Comprehensive Income		$ 72,894,392	$ 74,760,681	147,568,765	$ 140,835,188
Balance at end of period		7,139,902	17,517,734	7,139,902	17,517,734
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period		460,925	2,416,672	1,403,899	2,507,922
Other Comprehensive (loss) income before reclassifications		300,767	(241,489)	(642,207)	(332,739)
Amounts reclassified from accumulated other comprehensive income		0	0	0	0
Comprehensive Income		300,767	(241,489)	(642,207)	(332,739)
Balance at end of period		761,692	2,175,183	761,692	2,175,183
Unrealized gains on available-for-sale securities:
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period		10,492,827	17,067,127	10,868,322	19,467,441
Other Comprehensive (loss) income before reclassifications		(3,186,497)	2,527,930	626,452	3,392,840
Amounts reclassified from accumulated other comprehensive income		1,245,234	(4,252,506)	(2,943,210)	(7,517,730)
Comprehensive Income		(1,941,263)	(1,724,576)	(2,316,758)	(4,124,890)
Balance at end of period		8,551,564	15,342,551	8,551,564	15,342,551
Unrealized gains (losses) on derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period		(2,149,805)	0	(959,206)	0
Other Comprehensive (loss) income before reclassifications		(23,549)	0	(1,214,148)	0
Amounts reclassified from accumulated other comprehensive income		0	0	0	0
Comprehensive Income		(23,549)	0	(1,214,148)	0
Balance at end of period		$ (2,173,354)	$ 0	$ (2,173,354)	$ 0

[1] Note: The condensed consolidated balance sheet at December 31, 2014 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.