Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Investment securities - held-to-maturity, fair value	$ 433,201	$ 507,699
Common stock, stated value	$ 1	$ 1
Authorized and unissued common shares reserved for issuance	150,000,000	150,000,000
Common stock, shares issued	101,179,000	94,654,000
Common stock, shares outstanding	101,179,000	94,654,000
Preferred Stock, Series A [Member]
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares sold	0	0
Preferred stock, shares outstanding	0	0