Capital Stock (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Warrant or Right [Line Items]
Common stock authorized (in shares)	150,000,000
Preferred stock authorized (in shares)	4,000,000
Common stock, par value	$ 1.25	$ 1.25
Preferred stock authorized, par value (in dollars per share)	$ 1.25
Shares Authorized to Be Purchased [Roll Forward]
Shares Purchased			0
Treasury Stock
Shares Authorized to Be Purchased [Roll Forward]
Shares Purchased	0	0	596,632
Preferred Stock Purchase Rights Agreement
Class of Warrant or Right [Line Items]
Number of securities called by rights (in shares)	0.01