Long-term Debt (Details) (USD $)														12 Months Ended						12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Buildings [Member]	Dec. 31, 2010 Buildings [Member]	Dec. 31, 2011 Vehicles [Member]	Dec. 31, 2010 Vehicles [Member]	Dec. 31, 2011 Machinery and Equipment [Member]	Dec. 31, 2010 Machinery and Equipment [Member]	Dec. 31, 2011 Capital Leases Member	Dec. 31, 2011 Other Long-term Debt Member	Dec. 31, 2011 Revolving Facility [Member]	Dec. 31, 2010 Revolving Facility [Member]	Dec. 31, 2011 Private Placement [Member]	Dec. 31, 2010 Private Placement [Member]	Dec. 31, 2011 Private Placement [Member] Private Placement Notes Series A [Member]	Dec. 31, 2011 Private Placement [Member] Private Placement Notes Series B [Member]	Dec. 31, 2011 Other Non-US Dollar-denominated Facilities [Member]	Dec. 31, 2010 Other Non-US Dollar-denominated Facilities [Member]	Dec. 31, 2011 Dominion Terminal Associates Bonds [Member]	Dec. 31, 2010 Dominion Terminal Associates Bonds [Member]	Dec. 31, 2011 Captial Lease Interest Rate Information [Member]	Dec. 31, 2010 Captial Lease Interest Rate Information [Member]
Long-term Debt Types [Abstract]
Bank Credit Facility												$ 110,000,000	$ 217,200,000	$ 100,000,000	$ 0			$ 15,400,000	$ 28,100,000
Dominion Terminal Associates Bonds																				43,200,000	43,200,000
Captial lease arrangments	43,000,000	33,900,000	13,400,000																			95,400,000	64,200,000
Total Long-Term Debt	364,000,000	352,700,000
Long Term Debt By Current And Noncurrent [Abstract]
Current maturities of long-term debt	28,700,000	29,000,000
Long-term debt	335,300,000	323,700,000
Total Long-Term Debt	364,000,000	352,700,000
Interest Rate And Other Disclosures [Abstract]
Average Interest Rate												2.10%	2.10%			4.57%	5.20%	6.90%	5.70%	6.00%		4.30%	4.30%
Debt Due Date														Jan. 01, 2021						Jan. 01, 2033
Minimum Repayments of Long-term Debt [Line Items]
2012	28,700									21,600	7,100
2013	20,800									18,300	2,500
2014	114,400									16,700	97,700
2015	22,800									14,900	7,900
2016	21,600									13,700	7,900
Later years	155,700									10,200	145,500
Borrowed Funds	364,000									95,400	268,600
Captial Leases [Line Items]
Capital Leased Assets Gross	133,200	88,900		6,000	8,800	89,900	54,800	37,300	25,300
Accumulated Amortization	30,000	21,700
Total	$ 103,200	$ 67,200