Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Investment securities [Abstract]
Investment Securities, fair value	$ 515,675	$ 565,493	$ 599,062
Allowance for real estate and other repossessed assets - Accounts 1953055, 1953056, 1953555	$ 8,576	$ 9,562	$ 9,448
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)	75,089,152	74,993,407	74,817,155
Common stock, shares outstanding (in shares)	75,089,152	74,993,407	74,817,155
Treasury stock, shares at cost (in shares)	9,672,749	9,655,975	8,950,838