Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investment securities [Abstract]
Investment securities, fair value	$ 565,493	$ 629,159
Real estate and other repossessed assets, allowance	$ 9,562	$ 12,622
Shareholders' equity: [Abstract]
Common stock, par value (in dollars per share)	$ 0.00006	$ 0.00006
Common stock, authorized (in shares)	2,500,000,000	2,500,000,000
Common stock, shares issued (in shares)	74,993,407	74,530,364
Common stock, shares outstanding (in shares)	74,993,407	74,530,364
Treasury stock, shares at cost (in shares)	9,655,975	8,636,332