Shareholders' Equity and Earnings Per Common Share, Earings Per Share Reconciliation (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share Reconciliation [Abstract]
Net income		$ 12,388	$ 14,772	$ 34,425	$ 19,582
Weighted average shares outstanding (in shares)	[1]	21,750,000	21,891,000	21,788,000	22,081,000
Stock units for deferred compensation plan for non-employee directors (in shares)		113,000	109,000	118,000	119,000
Effect of stock options (in shares)		70,000	84,000	76,000	92,000
Performance share units (in shares)		34,000	29,000	32,000	33,000
Weighted average shares outstanding for calculation of diluted earnings per share (in shares)		21,967,000	22,113,000	22,014,000	22,325,000
Net income per common share [Abstract]
Basic (in dollars per share)	[1]	$ 0.57	$ 0.67	$ 1.58	$ 0.89
Diluted (in dollars per share)		$ 0.56	$ 0.67	$ 1.56	$ 0.88
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.