Long-term Debt (Details) (USD $)														12 Months Ended						12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Buildings [Member]	Dec. 31, 2011 Buildings [Member]	Dec. 31, 2012 Vehicles [Member]	Dec. 31, 2011 Vehicles [Member]	Dec. 31, 2012 Machinery and Equipment [Member]	Dec. 31, 2011 Machinery and Equipment [Member]	Dec. 31, 2012 Capital Leases Member	Dec. 31, 2012 Other Long-term Debt Member	Dec. 31, 2012 Revolving Facility [Member]	Dec. 31, 2011 Revolving Facility [Member]	Dec. 31, 2012 Private Placement [Member]	Dec. 31, 2011 Private Placement [Member]	Dec. 31, 2012 Private Placement [Member] Private Placement Notes Seriesa [Member]	Dec. 31, 2012 Private Placement [Member] Private Placement Notes Series B [Member]	Dec. 31, 2012 Other Non-US Dollar-denominated Facilities [Member]	Dec. 31, 2011 Other Non-US Dollar-denominated Facilities [Member]	Dec. 31, 2012 Dominion Terminal Associates Bonds [Member]	Dec. 31, 2011 Dominion Terminal Associates Bonds [Member]	Dec. 31, 2012 Captial Lease Interest Rate Information [Member]	Dec. 31, 2011 Captial Lease Interest Rate Information [Member]
Long-term Debt Types [Abstract]
Bank Credit Facility												$ 107,200,000	$ 110,000,000	$ 100,000,000	$ 100,000,000			$ 20,900,000	$ 15,400,000
Dominion Terminal Associates Bonds																				43,200,000	43,200,000
Captial lease arrangments	18,100,000	43,000,000	33,900,000																			91,300,000	95,400,000
Total Long-Term Debt	362,600,000	364,000,000
Long Term Debt By Current And Noncurrent [Abstract]
Current maturities of long-term debt	27,000,000	28,700,000
Long-term debt	335,600,000	335,300,000
Total Long-Term Debt	362,600,000	364,000,000
Interest Rate And Other Disclosures [Abstract]
Average Interest Rate												1.50%	2.10%			4.57%	5.20%	6.30%	6.90%	6.00%		4.20%	4.30%
Debt Due Date														Jan. 01, 2021						Jan. 01, 2033
Minimum Repayments of Long-term Debt [Line Items]
2013	27,000									20,900	6,100
2014	28,800									19,100	9,700
2015	27,300									17,700	9,600
2016	21,200									13,300	7,900
2017	124,900									10,200	114,700
Later years	133,400									10,100	123,300
Borrowed Funds	362,600									91,300	271,300
Captial Leases [Line Items]
Capital Leased Assets Gross	149,600	133,200		4,900	6,000	108,200	89,900	36,500	37,300
Accumulated Amortization	47,400	30,000
Total	$ 102,200	$ 103,200