Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Securities, market value	$ 607,626	$ 744,432	$ 579,737
Common stock, par value	$ 1	$ 1	$ 1
Common stock, shares authorized	20,000,000	20,000,000	20,000,000
Common stock, shares issued	15,125,541	15,368,717	15,358,672
Common stock, shares outstanding	15,125,541	15,368,717	15,358,672
Accumulated other comprehensive income, tax	$ 5,484	$ 4,551	$ 5,797
Senior Preferred Stock [Member]
Preferred stock, par value	$ 1	$ 1	$ 1
Preferred stock, shares authorized	10,000,000	10,000,000	10,000,000
Preferred stock, shares issued	0	0	0
Cumulative Preferred Stock [Member]
Preferred stock, par value	$ 5	$ 5	$ 5
Preferred stock, shares authorized	900,000	900,000	900,000
Preferred stock, shares issued	0	0	0