Income Taxes (Schedule Of Deferred Income Tax Liabilities And Assets) (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Jun. 30, 2019
Components Of Deferred Income Tax (Liabilities)/Assets [Abstract]
Deferred income tax liabilities - property	$ (12,474,000,000)	$ (12,184,000,000)
Deferred income tax liabilities operating lease assets	397,000,000	447,000,000
Deferred income tax liabilities - other	(444,000,000)	(341,000,000)
Total deferred income tax liabilities	(13,315,000,000)	(12,972,000,000)
Deferred income tax asset - accrued wages	40,000,000	45,000,000
Deferred income tax asset - accrued casualty costs	143,000,000	146,000,000
Deferred income tax asset - stock compensation	26,000,000	37,000,000
Deferred income tax asset - retiree benefits	255,000,000	171,000,000
Deferred income tax asset - operating lease liabiities	396,000,000	453,000,000
Deferred income tax asset - other	208,000,000	128,000,000
Total deferred income tax asset	1,068,000,000	980,000,000	$ 23,000,000
Net deferred income tax liability	(12,247,000,000)	(11,992,000,000)
Income Tax Details [Abstract]
Deferred tax valuation allowance	$ 0	$ 0

The tax effect as of the balance sheet date of the amount of estimated future tax deductions arising from operating lease liabilities, which can only be deducted for tax purposes when actual costs are incurred, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken.

No definition available.