Consolidated Balance Sheets (Parenthetical) (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Investment securities [Abstract]
Investment securities, fair value	$ 676,445	$ 687,127	$ 654,479
Real estate and other repossessed assets, Valuation allowance	$ 25,916	$ 24,195	$ 26,910
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)	73,964,496	73,163,275	73,089,764
Common stock, shares outstanding (in shares)	73,964,496	73,163,275	73,089,764
Treasury stock, shares at cost (in shares)	4,626,998	4,304,782	4,302,180