Income Taxes - Summary of Changes in Unrecognized Tax Benefits (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at beginning of year	$ 59,404,900	$ 7,343,500	$ 3,951,100
Increases resulting from tax positions taken during a prior period	3,456,100	45,184,200	573,900
Decreases resulting from tax positions taken during a prior period	(10,120,900)	0	0
Increases resulting from tax positions taken during the current period	3,447,300	7,712,500	2,818,500
Decreases related to settlements with taxing authorities	(7,481,200)	(235,700)	0
Reductions related to the lapse of statute of limitations	(1,596,900)	(599,600)	0
Unrecognized tax benefits at end of year	$ 47,109,300	$ 59,404,900	$ 7,343,500