Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Statement Of Financial Position [Abstract]
Securities held to maturity, fair values	$ 203,100	$ 211,498
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	31,917,385	31,917,385
Treasury stock, shares	2,225,604	2,427,640