Comprehensive Income (AOCI Rollforward) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$ 11,313,015	[1]
Comprehensive Income	74,674,373		66,074,507
Balance at end of period	8,803,947		19,483,799
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	1,403,899		2,507,922
Other Comprehensive (loss) income before reclassifications	(942,974)		(91,250)
Amounts reclassified from accumulated other comprehensive income	0		0
Comprehensive Income	(942,974)		(91,250)
Balance at end of period	460,925		2,416,672
Unrealized gains on available-for-sale securities:
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	10,868,322		19,467,441
Other Comprehensive (loss) income before reclassifications	(2,073,471)		864,910
Amounts reclassified from accumulated other comprehensive income	1,697,976		(3,265,224)
Comprehensive Income	(375,495)		(2,400,314)
Balance at end of period	10,492,827		17,067,127
Unrealized gains (losses) on derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(959,206)		0
Other Comprehensive (loss) income before reclassifications	0		0
Amounts reclassified from accumulated other comprehensive income	(1,190,599)		0
Comprehensive Income	(1,190,599)		0
Balance at end of period	$ (2,149,805)		$ 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.