Consolidated Balance Sheets (Parenthetical) (unaudited) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	[1]
Amortized cost of available-for-sale securities	$ 379,125	$ 354,924
Fair value of held-to-maturity securities	$ 151,935	$ 140,875
Preferred stock, shares authorized (shares)	10,000,000	10,000,000
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (shares)	2,500,000,000	2,500,000,000
Common stock, shares issued (shares)	24,292,615	24,185,923
Preferred stock Series A [Member]
Preferred stock, par value (in dollars per share)	$ 10.00	$ 10.00
Preferred stock, shares issued (shares)	51,500	51,500
Preferred stock, shares outstanding (shares)	0	0
Preferred Stock Series B [Member]
Preferred stock, shares authorized (shares)	250,000	250,000
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares issued (shares)	0	0
Preferred stock, shares outstanding (shares)	0	0

[1] Derived from audited consolidated financial statements