Schedule I - Financial Information of the Registrant (Parent Company) - Balance Sheets (Additional Information) (Details) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (USD per share)	$ 1	$ 1
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	24,071,508	24,071,683
Common stock, shares outstanding	23,719,347	23,719,522
Treasury stock, common shares	352,161	352,161
Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (USD per share)	$ 1	$ 1
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	24,071,508	24,071,683
Common stock, shares outstanding	23,719,347	23,719,522
Treasury stock, common shares	352,161	352,161