CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Unaudited) - USD ($)	Total	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), net [Member]
Balances at Mar. 31, 2016	$ 391,901,581	$ 138,835,064	$ 276,000,862	$ (22,934,345)
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Proceeds from exercise of stock options, including tax benefits	595,343	595,343
Stock Repurchased During Period, Value	4,995,809		4,995,809
Issuance of restricted common stock under stock option plan	1,320,036	1,320,036
Stock option expense	3,490,662	3,490,662
Other comprehensive income	(4,848,530)			(4,848,530)
Net income	73,600,294		73,600,294
Balances at Mar. 31, 2017	461,063,577	144,241,105	344,605,347	(27,782,875)
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Proceeds from exercise of stock options, including tax benefits	8,736,340	8,736,340
Stock Repurchased and Retired During Period, Value			4,614,331
Issuance of restricted common stock under stock option plan	655,620	655,620
Stock option expense	1,834,513	1,834,513
Other comprehensive income	(3,282,203)			(3,282,203)
Net income	24,547,248		24,547,248
Balances at Dec. 31, 2017	488,940,764	$ 157,872,907	$ 362,132,935	$ (31,065,078)
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (2,405,329)