Employment Benefit Plans Other Details (Details) number in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Multiemployer Plans [Line Items]
Collective bargaining agreements description	Under collective bargaining agreements, BNSF participates in multi-employer benefit plans that provide certain postretirement health care and life insurance benefits for eligible union employees. Health care claim payments and life insurance premiums paid attributable to retirees, which are generally expensed as incurred
Multiemployer Plan, insurance premiums paid	$ 64	$ 75	$ 61
Average number of employees covered under multi-employer benefit plans	37	35	36
Defined Contribution Plan Disclosure [Line Items]
Description of 401(k) plans and non-qualified defined contribution plan	BNSF sponsors qualified 401(k) plans that cover substantially all employees and a non-qualified defined contribution plan that covers certain officers and other employees. BNSF matched 75 percent of the first six percent of non-union employees’ contributions and matched 25 percent on the first four percent of a limited number of union employees’ contributions, which are subject to certain percentage limits of the employees’ earnings, at each pay period. Employer contributions are subject to a five-year length of service vesting schedule.
401(k) matching expense	$ 36	$ 35	$ 34
Retiree Health and Welfare Benefits [Member] | Funded Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer Contributions	14	29