Consolidated Balance Sheet Parenthetical - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Statement of Financial Position [Abstract]
Held-to-Maturity Securities, at Fair Value	$ 343,899	$ 343,751	$ 347,441
Preferred Stock, par value, in dollars per share	$ 5	$ 5	$ 5
Preferred Stock, shares authorized	1,000,000	1,000,000	1,000,000
Common Stock, par value, in dollars per share	$ 1	$ 1	$ 1
Common Stock, shares authorized	20,000,000	20,000,000	20,000,000
Common Stock, shares issued	18,481,301	17,943,201	17,943,201
Unallocated ESOP Shares ,in shares	20,050	19,466	38,396
Treasury Stock, in shares	4,570,291	4,441,093	4,479,257