Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Held-to-maturity, fair value	$ 466,578	$ 315,740	$ 303,961
Accumulated depreciation of premises and equipment	$ 112,530	$ 108,826	$ 104,225
Preferred stock, no par value
Preferred stock, shares authorized	2,000,000	200,000	200,000
Preferred stock, shares issued	0	0	0
Common stock, par value	$ 1	$ 1	$ 1
Common stock, shares authorized	60,000,000	45,000,000	45,000,000
Common stock, shares issued	38,110,136	32,774,420	32,760,088
Common stock, shares outstanding	38,110,136	32,774,420	32,760,088