Borrowings (Narrative) (Details) In Thousands, unless otherwise specified			9 Months Ended		9 Months Ended
	Sep. 30, 2013 Foreign Line of Credit [Member] USD ($)	Sep. 30, 2013 PNC Bank, N.A., Bank of America, N.A., Wells Fargo Bank, N.A. and Citizens Bank of Pennsylvania [Member] Letter of Credit [Member] USD ($)	Sep. 30, 2013 PNC Bank, N.A., Bank of America, N.A., Wells Fargo Bank, N.A. and Citizens Bank of Pennsylvania [Member] Revolving Credit Facility [Member] USD ($)	Dec. 31, 2012 PNC Bank, N.A., Bank of America, N.A., Wells Fargo Bank, N.A. and Citizens Bank of Pennsylvania [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2013 NatWest Bank [Member] Foreign Line of Credit [Member] USD ($)	Sep. 30, 2013 NatWest Bank [Member] Foreign Line of Credit [Member] GBP (£)	Sep. 30, 2013 NatWest Bank Outstanding Guarantees [Member] Foreign Line of Credit [Member] USD ($)
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 15,000		$ 125,000		$ 2,428	£ 1,500
Line of Credit Facility, Description			This Credit Agreement replaced a prior revolving credit facility with a maximum credit line of $90,000 and a $20,000 term loan.
Line of Credit Facility, Borrowing Capacity, Description			The Credit Agreement provides for a five-year, unsecured revolving credit facility that permits borrowing up to $125,000 for the U.S. borrowers and a sublimit of the equivalent of $15,000 U.S. dollars that is available to the Canadian borrowers.
Line of Credit Facility, Provision for Increase in Capacity			50,000
Line of Credit Facility, Capacity Available for Trade Purchases			20,000
Line of Credit Facility, Interest Rate Description			Borrowings under the Credit Agreement will bear interest at rates based upon either the base rate or LIBOR-based rate plus applicable margins. Applicable margins are dictated by the ratio of the Company's indebtedness, less cash on hand in excess of $15,000, to the Company's consolidated EBITDA, as defined in the underlying Credit Agreement. The base rate is the highest of (a) PNC Bank's prime rate, (b) the Federal Funds Rate plus 0.50% or (c) the daily LIBOR rate, as defined in the underlying Credit Agreement, plus 1.00%. The base rate spread ranges from 0.00% to 1.00%. LIBOR-based rates are determined by dividing the published LIBOR rate by a number equal to 1.00 minus the percentage prescribed by the Federal Reserve for determining the maximum reserve requirements with respect to any Eurocurrency funding by banks on such day. The LIBOR-based rate spread ranges from 1.00% to 2.00%.		. The interest rate on this facility is the financial institution's base rate plus 1.50%.	. The interest rate on this facility is the financial institution's base rate plus 1.50%.
Line of Credit Facility, Covenant Terms			The Credit Agreement includes two financial covenants: (a) the Leverage Ratio, defined as the Company's Indebtedness, less cash on hand in excess of $15,000, divided by the Company's consolidated EBITDA, which must not exceed 3.00 to 1.00 and (b) Minimum Interest Coverage, defined as consolidated EBITDA less Capital Expenditures divided by consolidated interest expense, which must be no less than 3.00 to 1.00.
Line of Credit Facility, Dividend Restrictions			The Credit Agreement permits the Company to pay dividends and distributions and make redemptions with respect to its stock provided no event of default or potential default (as defined in the Credit Agreement) has occurred prior to or after giving effect to the dividend, distribution, or redemption. Dividends, distributions, and redemptions are capped at $15,000 per year when funds are drawn on the facility. If no drawings on the facility exist, dividends, distributions, and redemptions in excess of $15,000 per year are subjected to a limitation of $75,000 in the aggregate. The $75,000 aggregate limitation also includes certain loans, investments, and acquisitions. The Company is permitted to acquire the stock or assets of other entities with limited restrictions, provided that the Leverage Ratio does not exceed 2.50 to 1.00 after giving effect to the acquisition.
Line of Credit Facility, Amount Outstanding		814	0	0			186
Line of Credit Facility, Current Borrowing Capacity			$ 124,186		$ 2,242
Line of Credit Facility, Collateral					This credit facility supports the subsidiary's working capital requirements and is collateralized by substantially all of the assets of its United Kingdom operations.	This credit facility supports the subsidiary's working capital requirements and is collateralized by substantially all of the assets of its United Kingdom operations.
Line of Credit Facility, Expiration Date					Jul. 31, 2014	Jul. 31, 2014
Line of Credit Facility, Asset Restrictions			Other restrictions exist at all times including, but not limited to, limitation of the Company's sale of assets, other indebtedness incurred by either the borrowers or the non-borrower subsidiaries of the Company, guaranties, and liens. On July 9, 2012, the Company amended the Credit Agreement to increase the limit applicable to the Company's sale of assets from $10,000 to $25,000.