Condensed Financial Information of Parent Company Only Disclosure (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Preferred Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00
Preferred Stock, Shares Authorized	100,000	100,000
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00
Common Stock, Shares Authorized	23,000,000	23,000,000
Common Stock, Shares, Issued	18,625,458	18,620,508
Common Stock, Shares, Outstanding	14,890,285	17,102,525
Treasury Stock, Shares	3,735,173	1,517,983
Parent Company
Preferred Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00
Preferred Stock, Shares Authorized	100,000	100,000
Preferred Stock, shares issued	0	0
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00
Common Stock, Shares Authorized	23,000,000	23,000,000
Common Stock, Shares, Issued	18,625,458	18,620,508
Common Stock, Shares, Outstanding	14,890,285	17,102,525
Treasury Stock, Shares	3,735,173	1,517,983
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	$ 12,100	$ 29,800	$ 0