Consolidated Balance Sheets (Parenthetical) (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Investment securities [Abstract]
Investment securities, fair value	$ 670,811	$ 687,127	$ 625,705
Real estate and other repossessed assets, Valuation allowance	$ 22,530	$ 24,195	$ 26,857
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)	73,896,899	73,163,275	73,029,101
Common stock, shares outstanding (in shares)	73,896,899	73,163,275	73,029,101
Treasury stock, shares at cost (in shares)	4,610,898	4,304,782	4,289,893