Stock and Other Incentive Plans - Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock Options Outstanding:
Options outstanding, beginning of year (shares)	328,533	318,100	316,321
Granted (shares)	235,572	203,836	206,824
Exercised (shares)	(35,277)	(16,716)	(32,076)
Forfeited (shares)	(54,095)	(40,897)	(40,659)
Expired (shares)	(142,074)	(135,790)	(132,310)
Outstanding, end of period (shares)	332,659	328,533	318,100
Weighted-average exercise price:
Options outstanding, beginning of year (in USD per share)	$ 24.17	$ 25.00	$ 23.69
Options granted during the year (in USD per share)	24.17	27.30	25.77
Options exercised during the year (in USD per share)	25.01	24.01	24.31
Options forfeited during the year (in USD per share)	25.26	24.06	25.01
Options expired during the year (in USD per share)	25.77	23.55	23.22
Options outstanding, end of year (in USD per share)	25.59	24.17	25.00
Weighted-average fair value of options granted during the year (calculated as of the grant date) (in USD per share)	$ 7.02	$ 7.81	$ 6.31
Intrinsic value of options exercised during the year	$ 269	$ 71	$ 271
Intrinsic value of options outstanding (calculated as of December 31)	$ 2,589	$ 1,402	$ 2,683
Exercise prices of options outstanding (calculated as of December 31) (in USD per share)	$ 25.59	$ 24.17	$ 25.00
Weighted-average contractual life of outstanding options (calculated as of December 31, in years)	24 days	24 days	24 days