Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common stock [Member]	Additional paid-in capital [Member]	Retained earnings [Member]	Treasury stock [Member]	Accumulated other comprehensive income (loss), net [Member]	Total
Balance in the beginning at Dec. 31, 2016	$ 514	$ 984,087	$ 55,454	$ (502,104)	$ (1,762)	$ 536,189
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			8,258			8,258
Stock-based compensation		902				902
Issuance under purchase and equity compensation plans, including (gain) loss on reissuance of treasury stock		(11,314)		5,577		(5,737)
Cash dividends declared			(1,900)			(1,900)
Warrant exercise		(1,933)		1,933
Other comprehensive income (loss)					(94)	(94)
Balance in the ending at Mar. 31, 2017	514	971,742	61,812	(494,594)	(1,856)	537,618
Balance in the beginning at Dec. 31, 2017	515	970,668	60,795	(493,329)	(6,242)	532,407
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			8,464			8,464
Stock-based compensation		833				833
Issuance under purchase and equity compensation plans, including (gain) loss on reissuance of treasury stock		(1,476)		5,319		3,843
Reissuance of treasury stock for Peoples acquisition		42,243		67,970		110,213
Cash dividends declared			(2,756)			(2,756)
Reclassificaiton of tax effects from ASU 2018-02			1,479		(1,479)
Cumulative effect adjustment from ASU 2017-02			26			26
Other comprehensive income (loss)					(7,167)	(7,167)
Balance in the ending at Mar. 31, 2018	$ 515	$ 1,012,268	$ 68,008	$ (420,040)	$ (14,888)	$ 645,863