Significant Accounting Policies (Estimated Useful Lives Of Property And Equipment) (Details)	12 Months Ended
	Dec. 31, 2012
Structures [Member]
Significant Accounting Policies [Line Items]
Estimated minimum useful lives of asset, years	7
Estimated maximum useful lives of asset, years	30
Revenue Equipment [Member]
Significant Accounting Policies [Line Items]
Estimated minimum useful lives of asset, years	4
Estimated maximum useful lives of asset, years	15
Other Equipment [Member]
Significant Accounting Policies [Line Items]
Estimated minimum useful lives of asset, years	2
Estimated maximum useful lives of asset, years	20
Leasehold Improvements [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of assets	Lesser of economic life or life of lease