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, 2010	$ 170,548,000	$ 136,000	$ 128,061,000	$ 226,114,000	$ 36,287,000	$ 561,146,000
Balance (in Shares) at Dec. 31, 2010	10,840,608	13,637,258
Net income				32,335,000		32,335,000
Other comprehensive income					350,000	350,000
Stock-based compensation			1,753,000			1,753,000
Tax benefit (expense) from exercise of stock options			120,000			120,000
Shares of Stock Issued from Stock Option Exercise (in Shares)		194,234
Value of Stock Issued from Stock Option Exercise		2,000	7,150,000			7,152,000
Shares issued in conversion of preferred stock to common stock	(33,000)		33,000
Shares issued in conversion of preferred stock to common stock (in Shares)	(2,082)	503
Dividends declared to preferred stockholders				(4,336,000)		(4,336,000)
Dividends declared to common stockholders				(8,015,000)		(8,015,000)
Balance at Jun. 30, 2011	170,515,000	138,000	137,117,000	246,098,000	36,637,000	590,505,000
Balance (in Shares) at Jun. 30, 2011	10,838,526	13,831,995
Balance at Dec. 31, 2011	170,515,000	138,000	139,183,000	265,198,000	36,702,000	611,736,000
Balance (in Shares) at Dec. 31, 2011	10,838,490	13,862,738
Net income				26,290,000		26,290,000
Other comprehensive income					7,961,000	7,961,000
Stock-based compensation			1,398,000			1,398,000
Tax benefit (expense) from exercise of stock options			(270,000)			(270,000)
Shares of Stock Issued from Stock Option Exercise (in Shares)		120,150				120,050
Value of Stock Issued from Stock Option Exercise		1,000	5,582,000			5,583,000
Shares issued in conversion of preferred stock to common stock	(1,000)		1,000
Shares issued in conversion of preferred stock to common stock (in Shares)	(78)	18
Dividends declared to preferred stockholders				(4,336,000)		(4,336,000)
Dividends declared to common stockholders				(8,390,000)		(8,390,000)
Balance at Jun. 30, 2012	$ 170,514,000	$ 139,000	$ 145,894,000	$ 278,762,000	$ 44,663,000	$ 639,972,000
Balance (in Shares) at Jun. 30, 2012	10,838,412	13,982,906