Components of Depreciation of Property Plant and Equipment (Detail)	12 Months Ended
	Dec. 31, 2012
Transportation equipment including capital leases
Property Plant and Equipment Estimated Useful Lives [Line Items]
Depreciation life in years	5 years
Equipment | Minimum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Depreciation life in years	10 years
Equipment | Maximum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Depreciation life in years	30 years
Software
Property Plant and Equipment Estimated Useful Lives [Line Items]
Depreciation life in years	5 years
Computers and IT equipment
Property Plant and Equipment Estimated Useful Lives [Line Items]
Depreciation life in years	3 years
Other equipment | Minimum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Depreciation life in years	2 years
Other equipment | Maximum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Depreciation life in years	10 years
Freehold buildings
Property Plant and Equipment Estimated Useful Lives [Line Items]
Depreciation life in years	40 years