Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Statement of Financial Position [Abstract]
Held to maturity, estimated fair value	$ 6,626	$ 6,699
Common stock, par value	$ 2.50	$ 2.50
Common stock, shares authorized	600,000,000	600,000,000
Common stock, shares issued	216,200,000	216,200,000
Treasury stock, shares	15,900,000	16,000,000