Common Stock (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, par value (in dollars per share)	$ 1	$ 1	$ 1
Common stock, shares issued (in shares)	37,200,698	37,198,298
Common stock, shares, outstanding	37,200,698	37,198,298
Common share purchase rights plan, expiration date	May 26, 2018
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Antidilutive stock options excluded from computation of earnings per share (in shares)	54,139	21,887	55,223