Commitments And Contingencies (Unused Letters Of Credit And Guarantee Agreements) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011
Letters of credit and guarantees, 2012	23,328,000
Letters of credit and guarantees, 2013	7,374,000
Letters of credit and guarantees, 2014	43,000
Letters of credit and guarantees, 2015	95,000
Letters of credit and guarantees, 2016	4,000
Letters of credit and guarantees, Thereafter	5,076,000
Performance Bonds, Environmental Guarantees And Insurance Claim Payment Guarantees [Member]
Outstanding letters of credit and guarantees	35,900,000
Maximum [Member] | Performance Bonds, Environmental Guarantees And Insurance Claim Payment Guarantees [Member]
Expiry date of outstanding letters of credit and guarantees	2020
Maximum [Member] | Guarantees Relating To Custom And Port Authorities [Member]
Expiry date of outstanding letters of credit and guarantees	three
Minimum [Member] | Performance Bonds, Environmental Guarantees And Insurance Claim Payment Guarantees [Member]
Expiry date of outstanding letters of credit and guarantees	2012
Minimum [Member] | Guarantees Relating To Custom And Port Authorities [Member]
Expiry date of outstanding letters of credit and guarantees	one