Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Investment securities [Abstract]
Investment Securities, fair value	$ 540,663	$ 565,493	$ 609,743
Allowance for real estate and other repossessed assets	$ 9,065	$ 9,562	$ 11,913
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)	75,080,768	74,993,407	74,800,772
Common stock, shares outstanding (in shares)	75,080,768	74,993,407	74,800,772
Treasury stock, shares at cost (in shares)	9,672,749	9,655,975	8,645,669