Consolidated Balance Sheets (Parenthetical) (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Investment securities [Abstract]
Investment securities, fair value	$ 654,479	$ 528,458	$ 460,358
Real estate and other repossessed assets, Valuation allowance	$ 26,910	$ 36,873	$ 35,979
Shareholders' equity: [Abstract]
Common stock, par value (in dollars per share)	$ 0.00006	$ 0.00006	$ 0.00006
Common stock, shares authorized (in shares)	2,500,000,000	2,500,000,000	2,500,000,000
Common stock, shares issued (in shares)	73,089,764	72,415,346	72,223,473
Common stock, shares outstanding (in shares)	73,089,764	72,415,346	72,223,473
Treasury stock, shares at cost (in shares)	4,302,180	4,087,995	4,008,119