Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Investment securities:
Held-to-maturity, fair values	$ 177,532	$ 161,877
Stockholders' equity:
Nonvoting noncumulative preferred stock, par value
Nonvoting noncumulative preferred stock, authorized shares	100,000	100,000
Nonvoting noncumulative preferred stock, issued shares	5,000	5,000
Nonvoting noncumulative preferred stock, outstanding shares	5,000	5,000