Commitments And Contingencies (Details)	9 Months Ended
	Sep. 30, 2015 USD ($) location	Dec. 31, 2014 USD ($) location
Commitments and Contingencies Disclosure [Abstract]
Environmental liability	$ 70,000,000	$ 66,000,000
Current environmental liability	$ 15,000,000	$ 15,000,000
Known cleanup and remediation locations and projects | location	145	146
Number of sites - representative sample | location	15
Liability associated with those sites	$ 42,000,000
Environmental locations representative sample liability payout period, in years	5 years
Responsible locations with another party | location	12
Self-insured injury/damage to third party - up to	$ 50,000,000
Self-insured injury/damage to third parties - and above, per occurrence	1,200,000,000.0
Self-insured NS owned property - up to	25,000,000
Self-insured NS owned property - and above, per occurrence	200,000,000
Purchase commitments, long-term service contracts	$ 852,000,000