Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Held to maturity, estimated fair value	$ 224	$ 319
Common stock, par value	$ 2.50	$ 2.50
Common stock, shares authorized	600,000,000	600,000,000
Common stock, shares issued	217,600,000	216,800,000
Treasury stock, shares	25,300,000	17,600,000