Consolidated Statements of Financial Position (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Held-to-maturity, fair value	$ 229,922	$ 183,769
Preferred stock, no par value	$ 0	$ 0
Preferred stock, shares authorized	200,000	200,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	45,000,000	45,000,000
Common stock, shares issued	27,498,868	27,456,907
Common stock, shares outstanding	27,498,868	27,456,907