Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Statement of Financial Position [Abstract]
Held-to-maturity securities, at fair value	$ 266,068	$ 280,338	$ 292,605
Preferred Stock, par value (in dollars per share)	$ 1	$ 5	$ 5
Preferred Stock, shares authorized (in shares)	1,000,000	1,000,000	1,000,000
Common Stock, par value (in dollars per share)	$ 1	$ 1	$ 1
Common Stock, shares authorized (in shares)	30,000,000	20,000,000	20,000,000
Common Stock, shares issued (in shares)	19,035,565	19,035,565	18,481,301
Unallocated ESOP Shares (in shares)	5,001	5,001	9,643
Treasury Stock (in shares)	4,517,412	4,558,207	4,467,909