CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Allowance for credit losses	$ 34,119	$ 16,202
Preferred stock, par value (in USD per share)	$ 5.00	$ 5.00
Preferred stock, shares authorized (in shares)	15,000,000	15,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in USD per share)	$ 1.00	$ 1.00
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	12,908,097	12,905,097
Common stock, shares outstanding (in shares)	11,013,804	11,547,443
Treasury stock (in shares)	1,894,293	1,357,654