Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Held-to-maturity, fair value	$ 499,904	$ 315,740	$ 314,275
Accumulated depreciation of premises and equipment	$ 117,566	$ 108,826	$ 106,418
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	38,130,965	32,774,420	32,762,591
Common stock, shares outstanding	38,130,965	32,774,420	32,762,591