Income Taxes (Schedule Of Deferred Income Tax Liabilities And Assets) (Details) - USD ($)	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Components Of Deferred Income Tax (Liabilities)/Assets [Abstract]
Deferred income tax liabilities - property	$ (12,184,000,000)		$ (11,590,000,000)
Deferred income tax liabilities - other	(341,000,000)		(213,000,000)
Total deferred income tax liabilities	(12,525,000,000)		(11,803,000,000)
Deferred income tax asset - accrued wages	45,000,000		46,000,000
Deferred income tax asset - accrued casualty costs	146,000,000		148,000,000
Deferred income tax asset - stock compensation	37,000,000		44,000,000
Deferred income tax asset - retiree benefits	171,000,000		138,000,000
Deferred income tax asset - other	134,000,000		125,000,000
Total deferred income tax asset	533,000,000	$ 23,000,000	501,000,000
Net deferred income tax liability	(11,992,000,000)		(11,302,000,000)
Income Tax Details [Abstract]
Deferred tax valuation allowance	$ 0		$ 0