Annual report pursuant to Section 13 and 15(d)

Nature Of Operations And Accounting Policies (Schedule Of Deferred Gain Activity) (Details)

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Nature Of Operations And Accounting Policies (Schedule Of Deferred Gain Activity) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Sale Leaseback and Financed Equipment Sales      
Deferred Revenue Arrangement [Line Items]      
Balance at beginning of period $ 74,774 $ 83,142 $ 95,601
Deferred gains arising from equipment sales 13,336 9,003 5,984
Amortization of deferred gains included in operating expenses as a reduction to rental expense 15,035 15,072 14,322
Amortization Of Deferred Gains Included In Gains On Asset Dispositions And Impairments, Net (602) (602) (2,454)
Other (5,954) (1,697) (1,667)
Balance at end of period 66,519 74,774 83,142
Fifty Percent Or Less Owned Subsidiaries      
Deferred Revenue Arrangement [Line Items]      
Balance at beginning of period 7,649 9,468 10,240
Amortization Of Deferred Gains Included In Gains On Asset Dispositions And Impairments, Net (1,715) (1,819) (772)
Balance at end of period $ 5,934 $ 7,649 $ 9,468