Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Investment securities [Abstract]
Investment Securities, Fair Value	$ 609,743	$ 629,159	$ 657,971
Real estate and other repossessed assets, Valuation allowance	$ 11,913	$ 12,622	$ 18,886
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)	74,800,772	74,530,364	74,351,392
Common stock, shares outstanding (in shares)	74,800,772	74,530,364	74,351,392
Treasury stock, shares at cost (in shares)	8,645,669	8,636,332	5,429,078