Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Statement of Financial Position [Abstract]
Held-to-maturity securities, at fair value	$ 233,501	$ 249,618	$ 259,128
Preferred Stock, par value (in dollars per share)	$ 1	$ 1	$ 1
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	30,000,000	30,000,000
Common Stock, shares issued (in shares)	20,194,474	20,194,474	19,606,449
Unallocated ESOP Shares (in shares)	0	0	5,151
Treasury Stock (in shares)	4,705,102	4,608,258	4,632,657