Operations and Summary of Significant Accounting Policies (Details 5) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013 item votepershare series rightpershare	Dec. 31, 2012	Dec. 31, 2011
Common Stock
Number of votes for each share of common stock held									1
Number of rights per common stock as a part of dividend distribution									1
Percentage acquisition of common stock triggering exercise terms of rights, minimum									15.00%
Ownership interest held by any stockholder at date of rights distribution to which additional exercise terms for the Rights distributed apply (as a percent)									25.00%
Subsequent increase in ownership interest held by any stockholder after rights distribution to which additional exercise terms for the Rights distributed apply (as a percent)									40.00%
Redemption price per right (in cents per right)									$ 0.01
Preferred Stock
Number of series by which the Board may issue authorized and unissued preferred stock, minimum									1
Reconciliation of basic earnings per share ("EPS") to diluted EPS
Net income available to common stockholders	$ 7,668	$ 20,006	$ 18,502	$ 4,795	$ 5,883	$ 12,976	$ 15,859	$ 7,201	$ 50,971	$ 41,918	$ 50,900
Basic weighted-average shares outstanding									48,521	48,339	48,974
Dilutive effect of potential common stock equivalents - stock options (in shares)									152	73	49
Diluted weighted-average shares outstanding									48,673	48,412	49,023
Net earnings per share:
Basic (in dollars per share)	$ 0.16	$ 0.41	$ 0.38	$ 0.10	$ 0.12	$ 0.27	$ 0.33	$ 0.15	$ 1.05	$ 0.87	$ 1.04
Diluted (in dollars per share)	$ 0.16	$ 0.41	$ 0.38	$ 0.10	$ 0.12	$ 0.27	$ 0.33	$ 0.15	$ 1.05	$ 0.87	$ 1.04
Potentially dilutive securities excluded from earnings per diluted share because their effect is anti-dilutive (in shares)										1,700	1,363
Comprehensive Income
Translation adjustments, net of tax	18,283				12,342				18,283	12,342
Unamortized pension adjustments, net of tax	(197)				(243)				(197)	(243)
Total accumulated other comprehensive income	18,086				12,099				18,086	12,099
Translation adjustments, tax									854	883
Unamortized pension adjustments, tax benefit									$ 43	$ 46
Concentration of Credit Risk
Number of banks where demand deposit or money market accounts are held by the company									11