Consolidated Balance Sheets (Parenthetical) (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Investment securities [Abstract]
Investment securities, fair value	$ 685,063	$ 687,127	$ 615,194
Real estate and other repossessed assets, Valuation allowance	$ 23,555	$ 24,195	$ 36,004
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)	73,547,801	73,163,275	72,945,798
Common stock, shares outstanding (in shares)	73,547,801	73,163,275	72,945,798
Treasury stock, shares at cost (in shares)	4,407,591	4,304,782	4,258,080