Annual report pursuant to Section 13 and 15(d)

Significant Accounting Policies (Estimated Useful Lives Of Property And Equipment) (Details)

v3.8.0.1
Significant Accounting Policies (Estimated Useful Lives Of Property And Equipment) (Details)
12 Months Ended
Dec. 31, 2017
Leasehold Improvements [Member]  
Significant Accounting Policies [Line Items]  
Estimated useful lives of assets Lesser of economic life or life of lease
Minimum [Member] | Structures [Member]  
Significant Accounting Policies [Line Items]  
Estimated useful lives of asset, years 7 years
Minimum [Member] | Revenue Equipment [Member]  
Significant Accounting Policies [Line Items]  
Estimated useful lives of asset, years 4 years
Minimum [Member] | Other Equipment [Member]  
Significant Accounting Policies [Line Items]  
Estimated useful lives of asset, years 2 years
Maximum [Member] | Structures [Member]  
Significant Accounting Policies [Line Items]  
Estimated useful lives of asset, years 30 years
Maximum [Member] | Revenue Equipment [Member]  
Significant Accounting Policies [Line Items]  
Estimated useful lives of asset, years 15 years
Maximum [Member] | Other Equipment [Member]  
Significant Accounting Policies [Line Items]  
Estimated useful lives of asset, years 20 years