Interim Condensed Consolidated Statements of Stockholders' Equity (unaudited) (USD $)	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2011	$ 170,515,000	$ 138,000	$ 139,183,000	$ 260,331,000	$ 36,702,000	$ 606,869,000
Balance (in Shares) at Dec. 31, 2011	10,838,490	13,862,738
Net income				12,654,000		12,654,000
Other comprehensive income					4,859,000	4,859,000
Stock-based compensation			543,000			543,000
Tax expense from exercise of stock options			3,000			3,000
Shares sold – options exercised		1,000	5,577,000			5,578,000
Shares sold – options exercised (in Shares)		120,050
Dividends declared to preferred stockholders				(2,168,000)		(2,168,000)
Dividends declared to common stockholders				(4,195,000)		(4,195,000)
Balance at Mar. 31, 2012	170,515,000	139,000	145,306,000	266,622,000	41,561,000	624,143,000
Balance (in Shares) at Mar. 31, 2012	10,838,490	13,982,788
Balance at Dec. 31, 2012	170,514,000	141,000	154,692,000	279,993,000	50,808,000	656,148,000
Balance (in Shares) at Dec. 31, 2012	10,838,412	14,158,127
Net income				13,805,000		13,805,000
Other comprehensive income					9,444,000	9,444,000
Stock-based compensation			498,000			498,000
Repurchase of common stock		(1,000)	(4,699,000)			(4,700,000)
Repurchase of common stock (in Shares)		(100,000)				(100,000)
Shares issued in conversion of preferred stock to common stock	(2,000)		2,000
Shares issued in conversion of preferred stock to common stock (in Shares)	(107)	25
Dividends declared to preferred stockholders				(2,168,000)		(2,168,000)
Dividends declared to common stockholders				(4,217,000)		(4,217,000)
Balance at Mar. 31, 2013	$ 170,512,000	$ 140,000	$ 150,493,000	$ 287,413,000	$ 60,252,000	$ 668,810,000
Balance (in Shares) at Mar. 31, 2013	10,838,305	14,058,152