CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($)	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income, Net of Tax [Member] Available-for-sale Securities [Member]	Treasury Stock [Member]
Balance at beginning of period at Dec. 31, 2014		$ 28,159,000	$ 225,015,000	$ 118,412,000	$ 6,098,000	$ (11,656,000)
Balance at beginning of period, shares at Dec. 31, 2014		28,159,027				(1,385,164)
Issuance of common stock		$ 5,320,000	109,569,000
Issuance of common stock ,shares		5,320,000
Issuance of restricted shares		$ 71,000	(71,000)
Issuance of restricted shares, shares		71,000
Cancellation of restricted shares		$ 0	0
Cancellation of restricted shares, shares		0
Proceeds from exercise of stock options		$ 60,000	946,000
Proceeds from exercise of stock options, shares		59,867
Stock-based compensation			1,140,000
Dividends on common shares				(4,829,000)
Purchase of treasury shares						$ (732,000)
Purchase of treasury shares,shares						(28,613)
Net income	$ 26,699,000			26,699,000
Other comprehensive income during the period	(1,901,000)				(1,901)
Balance at end of period at Sep. 30, 2015	502,300,000	$ 33,610,000	336,599,000	140,282,000	4,197,000	$ (12,388,000)
Balance at end of period, shares at Sep. 30, 2015		33,609,894				(1,413,777)
Balance at beginning of period at Dec. 31, 2015	514,759,000	$ 33,625,000	337,349,000	152,820,000	3,353,000	$ (12,388,000)
Balance at beginning of period, shares at Dec. 31, 2015		33,625,162				(1,413,777)
Issuance of common stock		$ 2,549,000	69,906,000
Issuance of common stock ,shares		2,549,469
Issuance of restricted shares		$ 126,000	(126,000)
Issuance of restricted shares, shares		125,581
Cancellation of restricted shares		$ (7,000)	7,000
Cancellation of restricted shares, shares		(7,085)
Proceeds from exercise of stock options		$ 55,000	908,000
Proceeds from exercise of stock options, shares		54,510
Stock-based compensation			1,586,000
Dividends on common shares				(6,974,000)
Purchase of treasury shares						$ (1,225,000)
Purchase of treasury shares,shares						(42,556)
Net income	53,923,000			53,923,000
Other comprehensive income during the period	7,096,000				7,096,000
Balance at end of period at Sep. 30, 2016	$ 642,583,000	$ 36,348,000	$ 409,630,000	$ 199,769,000	$ 10,449,000	$ (13,613,000)
Balance at end of period, shares at Sep. 30, 2016		36,347,637				(1,456,333)