Debt (Details)	12 Months Ended										12 Months Ended
	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2014 London Interbank Offered Rate (LIBOR) [Member]	Dec. 31, 2014 Base Rate [Member]	Dec. 31, 2014 Canadian Dealer Offered Rate [Member]	Dec. 31, 2014 Federal Funds Rate [Member]	Dec. 31, 2014 Commercial Paper [Member]	Dec. 31, 2014 Unsecured Syndicated Senior Credit Facility [Member] USD ($)	Dec. 31, 2013 Unsecured Syndicated Senior Credit Facility [Member] USD ($)	Dec. 31, 2014 Receivables Securitization Facility [Member] USD ($)	Dec. 31, 2013 Receivables Securitization Facility [Member] USD ($)	Feb. 12, 2012 Floating Rate Senior Notes [Member] USD ($)	Dec. 31, 2014 Australian Seasonal Credit Facility [Member] USD ($)	Dec. 31, 2014 Australian Seasonal Credit Facility [Member] AUD
Current portion [Abstract]
Other Long-term Debt, Current														$ 1,529,000
Long-term portion [Abstract]
Long-term Line of Credit, Noncurrent									251,709,000	194,418,000
Receivable Securitization Facility											67,600,000	52,000,000
Total long-term portion	319,309,000	246,418,000
Floating Rate Senior Notes													100,000,000
Total debt	320,838,000	246,418,000
Debt
Revolving credit facility, maximum borrowing capacity									465,000,000						3,000,000
Revolving credit facility, term (in years)									5 years
Debt Instrument, Maturity Date									Nov. 20, 2019
Potential increase in borrowing capacity									75,000,000
Line of Credit Facility, Amount Outstanding									251,709,000
Line of credit facility, remaining borrowing capacity									209,542,000
Weighted average effective interest rate (in hundredths)									2.00%
Debt Instrument, Basis Spread on Variable Rate				1.00%		1.00%	0.50%	0.75%
Debt Instrument, Interest Rate Margins on Variable Rates, Minimum				1.15%	0.15%	1.15%
Debt Instrument, Interest Rate Margins on Variable Rate, Maximum				1.65%	0.65%	1.65%
Annual facility fee, minimum (in hundredths)									0.10%
Annual facility fee, maximum (in hundredths)									0.225%
Receivables Facility, Borrowing Capacity May to June											140,000,000
Receivables Facility, Borrowing Capacity March to April and July to Sept											120,000,000
Receivables Facility, Borrowing Capacity Oct to February											70,000,000
Receivables Facility, Term (in years)											2 years
Additional Seasonal Borrowing Capacity											40,000,000
Receivable Securitization Facility											67,600,000	52,000,000
Weighted average effective interest rate											0.90%
Receivables facility, unused fee											0.35%
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	4,099,000	3,055,000
Financing costs deferred	394,000	1,044,000	0
Write-off fully amortized deferred financing costs	0	0
Balance at end of year	4,493,000	4,099,000	3,055,000
Accumulated amortization of deferred financing costs [Abstract]
Balance at beginning of year	(1,985,000)	(1,573,000)
Amortization of deferred financing costs	(542,000)	(412,000)
Write Off Of Accumulated Amortized Deferred Financing Costs	0	0
Balance at end of year	(2,527,000)	(1,985,000)	(1,573,000)
Deferred financing costs, net of accumulated amortization	$ 1,966,000	$ 2,114,000