Consolidated Balance Sheets (Parenthetical)	12 Months Ended
	Dec. 31, 2018 $ / shares shares	Dec. 31, 2017 $ / shares shares
Stock split, conversion ratio	2
Common stock, par value (in dollars per share) | $ / shares	$ 1.00	$ 1.00
Common stock, shares authorized	48,000,000	48,000,000
Redeemable stock, outstanding	5,642,154	6,467,027
Common stock, shares issued	37,271,606	36,446,890
Common stock, shares outstanding	37,272,000	36,447,000
Treasury stock, shares	20,033,108	18,692,901