Shareholders' Equity and Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended
		Nov. 15, 2011	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Apr. 26, 2016	Jan. 21, 2016
Class of Stock [Line Items]
Stock repurchased					$ 16,854	$ 9,025
Shareholders with certain limited exceptions		5.00%
Number of dividend preferred share purchase rights authorized for each outstanding common share held (in shares)		1
Number of Series C Junior participating preferred stock purchase by each right		1/1000
Beneficial ownership level		4.99%
Discount to current market price of the common stock		50.00%
Earnings Per Share Reconciliation [Abstract]
Net income			$ 6,373	$ 5,047	$ 16,911	$ 14,447
Weighted average shares outstanding (in shares)	[1]		21,232,000	22,673,000	21,421,000	22,852,000
Effect of stock options (in shares)			149,000	118,000	150,000	120,000
Stock units for deferred compensation plan for non-employee directors (in shares)			116,000	112,000	115,000	111,000
Restricted stock units (in shares)			0	230,000	46,000	283,000
Performance share units (in shares)			52,000	0	42,000	0
Weighted average shares outstanding for calculation of diluted earnings per share (in shares)			21,549,000	23,133,000	21,774,000	23,366,000
Net income per common share [Abstract]
Basic (in dollars per share)	[1]		$ 0.30	$ 0.22	$ 0.79	$ 0.63
Diluted (in dollars per share)			$ 0.30	$ 0.22	$ 0.78	$ 0.62
Common Stock [Member]
Class of Stock [Line Items]
Stock repurchase program percentage of shares authorized to be repurchased								5.00%
Stock repurchased (in shares)					1,153,136
Stock repurchased					$ 16,900
Stock repurchase program, remaining amount to be repurchased			$ 4,400		$ 4,400
Stock repurchase program, additional authorized amount							$ 5,000
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted loss per share (in shares)			30,000	30,000	30,000	30,000

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