CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred shares, par value	$ 0.01	$ 0.01
Preferred shares, shares authorized	5,000,000	5,000,000
Common stock, par value	$ 1.00	$ 1.00
Common stock, shares authorized	200,000,000	200,000,000
Treasury stock, shares	13,014,503	13,461,280
Common stock, shares, outstanding	59,411,636	58,964,859
Common stock, shares issued	72,426,139	72,426,139