Consolidated Statement of Stockholders' Equity - 3 months ended Mar. 31, 2016 - USD ($)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]
Shares outstanding at beginning of period (in shares) at Dec. 31, 2015		29,765,525		(37,937)
Stockholders' equity at beginning of period at Dec. 31, 2015	$ 395,249,574	$ 2,979	$ 319,002,254	$ (784,829)	$ 77,029,170
Increase (decrease) in stockholders' equity:
Share compensation expense	5,316,837		5,316,837
Exercise of stock options (in shares)		2,800
Exercise of stock options	34,188	$ 0	34,188
Common stock issued for vested restricted stock (in shares)		214,886
Common stock issued for vested restricted stock	0	$ 22	(22)
Common stock issued for vested performance shares (in shares)		37,547
Common stock issued for vested performance shares	0	$ 4	(4)
Common shares withheld and retired to satisfy employee tax witholding obligations upon vesting of restricted stock (in shares)		(79,229)
Common shares withheld and retired to satisfy employee tax withholding obligations upon vesting of share-based awards	(1,882,672)	$ (8)	(1,882,664)
Tax benefit from exercise of stock options			283,698
Treasury stock, shares, acquired				(910,908)
Treasury stock, value, acquired				$ (18,605,974)
Net income	262,611				262,611
Shares outstanding at end of period (in shares) at Mar. 31, 2016		29,941,529		(948,845)
Stockholders' equity at end of period at Mar. 31, 2016	$ 380,658,262	$ 2,997	$ 322,754,287	$ (19,390,803)	$ 77,291,781