Commitments and Contingencies (Details)	6 Months Ended
	Jun. 30, 2022 USD ($) location	Dec. 31, 2021 USD ($) location
Commitments and Contingencies Disclosure [Abstract]
Environmental liability	$ 56,000,000	$ 49,000,000
Current environmental liability	$ 15,000,000	$ 15,000,000
Known cleanup and remediation locations and projects | location	91	88
Number of sites - representative sample | location	19
Liability associated with those sites	$ 45,000,000
Environmental locations representative sample liability payout period, in years	5 years
Responsible locations with another party | location	8
Employees covered by collective bargaining agreements, percentage	80.00%
Self-insured injury/damage to third parties - and above, per occurrence	$ 75,000,000
Self-insured injury/damage to third party - up to	800,000,000
Self-insured injury/damage to third parties - and above, per occurrence for specific perils	$ 1,100,000,000
Percentage of potential losses covered	82.00%
Self-insured NS owned property - and above, per occurrence	$ 75,000,000
Self-insured NS owned property - up to	$ 275,000,000