Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Long-term portion [Abstract]
Total long-term portion	$ 246,418,000	$ 230,882,000
Total debt	246,418,000	230,882,000
Interest rate swap [Abstract]
Incremental interest expense arising from difference between interest paid and interest received related to swap agreements	1,379,000	1,292,000	3,600,000
Financial and other covenants [Abstract]
Financial covenants, dividend limitation as percent of preceding year's net income, maximum (in hundredths)	50.00%
Deferred financing costs [Abstract]
Balance at beginning of year	3,055,000	3,451,000
Financing costs deferred	1,044,000	0	1,674,000
Write-off fully amortized deferred financing costs	0	(396,000)
Balance at end of year	4,099,000	3,055,000	3,451,000
Accumulated amortization of deferred financing costs [Abstract]
Balance at beginning of year	(1,573,000)	(1,581,000)
Amortization of deferred financing costs	(412,000)	(388,000)
Write Off Of Accumulated Amortized Deferred Financing Costs	0	396,000
Balance at end of year	(1,985,000)	(1,573,000)	(1,581,000)
Deferred financing costs, net of accumulated amortization	2,114,000	1,482,000
Interest Rate Swap 1, Credit Facility [Member]
Interest rate swap [Abstract]
Interest rate swap agreement, fixed interest rate (in hundredths)	1.185%
Interest rate swap agreement, notional amount	25,000,000
Interest rate swap agreement, effective date	Nov. 21, 2011
Interest rate swap agreement, termination date	Oct. 19, 2016
Interest Rate Swap 2, Credit Facility [Member]
Interest rate swap [Abstract]
Interest rate swap agreement, fixed interest rate (in hundredths)	1.185%
Interest rate swap agreement, notional amount	25,000,000
Interest rate swap agreement, effective date	Nov. 21, 2011
Interest rate swap agreement, termination date	Oct. 19, 2016
Interest Rate Swap 3, Credit Facility [Member]
Interest rate swap [Abstract]
Interest rate swap agreement, fixed interest rate (in hundredths)	1.10%
Interest rate swap agreement, notional amount	50,000,000
Interest rate swap agreement, effective date	Dec. 21, 2011
Interest rate swap agreement, termination date	Oct. 19, 2016
Interest Rate Swap 4, Credit Facility [Member]
Interest rate swap [Abstract]
Interest rate swap agreement, fixed interest rate (in hundredths)	1.05%
Interest rate swap agreement, notional amount	25,000,000
Interest rate swap agreement, effective date	Jan. 17, 2012
Interest rate swap agreement, termination date	Oct. 19, 2016
Interest Rate Swap, Credit Facility [Member]
Interest rate swap [Abstract]
Interest rate swap agreement, fixed interest rate (in hundredths)	0.99%
Interest rate swap agreement, notional amount	25,000,000
Interest rate swap agreement, effective date	Jan. 19, 2012
Interest rate swap agreement, termination date	Oct. 19, 2016
Unsecured Syndicated Senior Credit Facility [Member]
Long-term portion [Abstract]
Long-term Line of Credit, Noncurrent	194,418,000	230,882,000
Debt
Revolving credit facility, maximum borrowing capacity	465,000,000
Revolving credit facility, term (in years)	5 years
Debt Instrument, Maturity Date	Sep. 20, 2018
Potential increase in borrowing capacity	75,000,000
Line of Credit Facility, Amount Outstanding	194,418,000
Line of credit facility, remaining borrowing capacity	267,357,000
Weighted average effective interest rate (in hundredths)	2.10%
Line of credit facility, interest rate description	Revolving borrowings under the Credit Facility bear interest, at our option, at either of the following and, in each case, plus an applicable margin:a base rate, which is the highest of (i) the Wells Fargo Bank, National Association prime rate, (ii) the Federal Funds Rate plus 0.500% and (iii) the London Interbank Offered Rate (LIBOR) Market Index Rate plus 1.000%; or LIBOR.Borrowings by the Canadian Borrower bear interest, at the Canadian Borrower’s option, at either of the following and, in each case, plus an applicable margin:a base rate, which is the greatest of (i) the Canadian Reference Bank prime rate and (ii) the annual rate of interest equal to the sum of the Canadian Dealer Offered Rate (CDOR) plus 1.000%; or CDOR. Borrowings by the Dutch Borrower bear interest at LIBOR plus an applicable margin.The interest rate margins on the borrowings and letters of credit are based on our leverage ratio and will range from 1.150% to 1.625% on CDOR, LIBOR and swingline loans, and from 0.150% to 0.625% on Base Rate and Canadian Base Rate loans.
Annual facility fee, minimum (in hundredths)	0.10%
Annual facility fee, maximum (in hundredths)	0.25%
Receivables Securitization Facility [Member]
Long-term portion [Abstract]
Receivable Securitization Facility	52,000,000	0
Debt
Receivables Facility, Borrowing Capacity March to August	120,000,000
Receivables Facility, Borrowing Capacity Sept to February	80,000,000
Receivables Facility, Term (in years)	2 years
Additional Seasonal Borrowing Capacity	40,000,000
Receivable Securitization Facility	52,000,000	0
Weighted average effective interest rate	0.90%
Receivables Facility, interest rate description	Depending on the funding source used by the financial institutions to purchase the receivables, borrowings under the Receivables Facility bear interest at one of the following and, in each case, plus an applicable margin of 0.75%:for financial institutions using the commercial paper market, commercial paper rates based on the applicable variable rates in the commercial paper market at the time of issuance;for financial institutions not using the commercial paper market, LMIR
Receivables facility, unused fee	0.35%
Floating Rate Senior Notes [Member]
Long-term portion [Abstract]
Floating Rate Senior Notes	$ 100,000,000