Consolidated Statements of Financial Position (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Held-to-maturity, fair value	$ 314,275	$ 268,271	$ 275,866
Accumulated depreciation of premises and equipment	$ 106,418	$ 100,261	$ 98,150
Preferred stock, no par value
Preferred stock, shares authorized	200,000	200,000	200,000
Preferred stock, shares issued	0	0	0
Common stock, par value	$ 1	$ 1	$ 1
Common stock, shares authorized	45,000,000	45,000,000	45,000,000
Common stock, shares issued	32,762,591	29,789,825	29,778,250
Common stock, shares outstanding	32,762,591	29,789,825	29,778,250