Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Shareholders' equity:
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized	80,000,000	80,000,000
Common stock, shares issued	33,744,385	35,829,549
Common stock, shares outstanding	33,744,385	35,829,549