Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Held to maturity, estimated fair value	$ 279	$ 319
Common stock, par value	$ 2.5	$ 2.5
Common stock, shares authorized	600,000,000	600,000,000
Common stock, shares issued	217,000,000	216,800,000
Treasury stock, shares	21,700,000	17,600,000