Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Preferred stock, par value (in dollars per share)	$ 25	$ 25
Preferred stock, shares authorized (in shares)	500,000	500,000
Preferred stock, shares issued (in shares)	0	0
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	19,047,548	19,047,548
Common stock, treasury shares (in shares)	3,855,971	3,280,040