Shareholders' Equity and Earnings Per Common Share, Earings Per Share Reconciliation (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share Reconciliation [Abstract]
Net income		$ 19,584	$ 12,445	$ 39,166	$ 32,556
Weighted average shares outstanding (in shares)	[1]	21,881,000	22,486,000	22,014,000	23,033,000
Stock units for deferred compensation plan for non-employee directors (in shares)		117,000	132,000	119,000	131,000
Effect of stock options (in shares)		85,000	110,000	90,000	116,000
Performance share units (in shares)		32,000	42,000	33,000	39,000
Weighted average shares outstanding for calculation of diluted earnings per share (in shares)		22,115,000	22,770,000	22,256,000	23,319,000
Net income per common share [Abstract]
Basic (in dollars per share)	[1]	$ 0.90	$ 0.55	$ 1.78	$ 1.41
Diluted (in dollars per share)		$ 0.89	$ 0.55	$ 1.76	$ 1.40
Stock Options [Member]
Antidilutive Securities [Abstract]
Antidilutive shares excluded from computation of diluted loss per share (in shares)		0	0	0	0

[1] Basic net income per common share includes weighted average common shares outstanding during the period and participating share awards.