CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common stock	Capital in excess of par value	Retained earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning Balance at Dec. 31, 2011	$ 160,852	$ 2,365	$ 56,214	$ 184,291	$ (16,618)	$ (65,400)
Beginning Balance (in shares) at Dec. 31, 2011		23,645
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16,806			16,806
Other comprehensive income (loss), net of tax	(1,748)				(1,748)
Stock repurchased	(3,998)					(3,998)
Stock issued under employee plans (in shares)		122
Stock issued under employee plans	972	12	960
Excess tax benefit on stock awards	211		211
Stock based compensation expense	1,149		1,149
Stock issued to directors (in shares)		18
Stock issued to directors	252	2	250
Ending Balance at Dec. 31, 2012	174,496	2,379	58,784	201,097	(18,366)	(69,398)
Ending Balance (in shares) at Dec. 31, 2012		23,785
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	19,155			19,155
Other comprehensive income (loss), net of tax	9,522				9,522
Stock repurchased	(6,617)					(6,617)
Stock issued under employee plans (in shares)		297
Stock issued under employee plans	1,497	30	1,467
Excess tax benefit on stock awards	271		271
Stock based compensation expense	1,511		1,511
Stock issued to directors (in shares)		16
Stock issued to directors	252	1	251
Ending Balance at Dec. 31, 2013	200,087	2,410	62,284	220,252	(8,844)	(76,015)
Ending Balance (in shares) at Dec. 31, 2013	24,098	24,098
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	21,847			21,847
Other comprehensive income (loss), net of tax	(15,317)				(15,317)
Stock repurchased	(748)					(748)
Stock issued under employee plans (in shares)		524
Stock issued under employee plans	2,457	52	2,405
Excess tax benefit on stock awards	1,486		1,486
Stock based compensation expense	2,535		2,535
Stock issued to directors (in shares)		9
Stock issued to directors	252	1	251
Ending Balance at Dec. 31, 2014	$ 212,599	$ 2,463	$ 68,961	$ 242,099	$ (24,161)	$ (76,763)
Ending Balance (in shares) at Dec. 31, 2014	24,631	24,631