Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Statement of Financial Position [Abstract]
Held-to-maturity securities, at fair value	$ 259,128	$ 280,338	$ 282,719
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)	19,606,449	19,035,565	19,035,565
Unallocated ESOP Shares (in shares)	5,151	5,001	9,932
Treasury Stock (in shares)	4,632,657	4,558,207	4,584,147