Employment Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2018

Dec. 31, 2017

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Benefit Costs

Components of the net (benefit) cost for certain employee benefit plans were as follows (in millions):

	Pension Benefits
	Year Ended			Year Ended			Year Ended
	December 31, 2018			December 31, 2017			December 31, 2016
Service cost	$	46		$	42		$	46
Interest cost	82			88			95
Expected return on plan assets	(157		)	(149		)	(142		)
Amortization of prior service credits	(1		)	—			(1		)
Amortization of net loss	1			—			1
Settlements	(1		)	—			(1		)
Net (benefit) cost recognized	$	(30	)	$	(19	)	$	(2	)

	Retiree Health and Welfare Benefits
	Year Ended			Year Ended			Year Ended
	December 31, 2018			December 31, 2017			December 31, 2016
Service cost	$	1		$	1		$	1
Interest cost	8			9			10
Amortization of prior service credits	(2		)	(2		)	(2		)
Amortization of net loss	—			—			1
Net (benefit) cost recognized	$	7		$	8		$	10

Schedule of Changes in Projected Benefit Obligations [Table Text Block]

The following tables show the change in projected benefit obligation (in millions):

	Pension Benefits
Change in Benefit Obligation	December 31, 2018			December 31, 2017
Projected benefit obligation at beginning of period	$	2,387		$	2,247
Service cost	46			42
Interest cost	82			88
Actuarial (gain) loss	(158		)	166
Benefits paid	(149		)	(144		)
Settlements	(10		)	(12		)
Projected benefit obligation at end of period	2,198			2,387
Component representing future salary increases	(136		)	(135		)
Accumulated benefit obligation at end of period	$	2,062		$	2,252

	Retiree Health and Welfare Benefits
Change in Benefit Obligation	December 31, 2018			December 31, 2017
Projected benefit obligation at beginning of period	$	241		$	237
Service cost	1			1
Interest cost	8			9
Plan participants’ contributions	4			4
Actuarial (gain) loss	(22		)	14
Benefits paid	(19		)	(23		)
Plan amendment	—			(1		)
Projected benefit obligation at end of period	$	213		$	241

Schedule of Changes in Fair Value of Plan Assets [Table Text Block]

The following tables show the change in plan assets of the plans (in millions):

	Pension Benefits
Change in Plan Assets	December 31, 2018			December 31, 2017
Fair value of plan assets at beginning of period	$	2,669		$	2,333
Actual return on plan assets	(189		)	479
Employer contributionsa	15			13
Benefits paid	(149		)	(144		)
Settlements	(10		)	(12		)
Fair value of plan assets at measurement date	$	2,336		$	2,669

^a  Employer contributions were classified as Other, Net under Operating Activities in the Company’s Consolidated Statements of Cash Flows.

	Retiree Health and Welfare Benefits
Change in Plan Assets	December 31, 2018			December 31, 2017
Fair value of plan assets at beginning of period	$	29		$	—
Employer contributionsa	—			48
Plan participants’ contributions	4			4
Benefits paid	(19		)	(23		)
Fair value of plan assets at measurement date	$	14		$	29

^a  Employer contributions were classified as Other, Net under Operating Activities in the Company’s Consolidated Statements of Cash Flows.

Schedule of Net Funded Status [Table Text Block]

The following table shows the funded status, defined as plan assets less the projected benefit obligation (in millions):

	Pension Benefits				Retiree Health and Welfare Benefits
	December 31, 2018		December 31, 2017		December 31, 2018			December 31, 2017
Funded status (plan assets less projected benefit obligations)	$	138	$	282	$	(199	)	$	(212	)

Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]

The following table shows the projected benefit obligation, accumulated benefit obligation, and fair value of plan assets for the three plans (in millions):

	December 31, 2018		December 31, 2017
Projected benefit obligation	$	138	$	157
Accumulated benefit obligation	$	138	$	157
Fair value of plan assets	$	36	$	43

Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]

The following tables show the pre-tax change in AOCI attributable to the components of the net cost and the change in benefit obligation (in millions):

	Pension Benefits
	Year Ended			Year Ended		Year Ended
Change in AOCI	December 31, 2018			December 31, 2017		December 31, 2016
Beginning balance	$	371		$	207	$	102
Amortization of net loss	1			—		1
Amortization of prior service credits	(1		)	—		(1		)
Actuarial gain (loss)	(188		)	164		106
Settlements	(1		)	—		(1		)
Ending balance	$	182		$	371	$	207

	Retiree Health and Welfare Benefits
	Year Ended			Year Ended			Year Ended
Change in AOCI	December 31, 2018			December 31, 2017			December 31, 2016
Beginning balance	$	(24	)	$	(9	)	$	(21	)
Amortization of net loss	—			—			1
Amortization of prior service credits	(2		)	(2		)	(2		)
Actuarial gain (loss)	22			(14		)	13
Prior service credits	—			1			—
Ending balance	$	(4	)	$	(24	)	$	(9	)

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

Pre-tax amounts currently recognized in AOCI consist of the following (in millions):

	Pension Benefits						Retiree Health and Welfare Benefits
	2018			2017			2018			2017
Net gain (loss)	$	183		$	370		$	(6	)	$	(28	)
Prior service credits	3			4			2			4
Settlements	(4		)	(3		)	—			—
Pre-tax amount recognized in AOCI at December 31,	$	182		$	371		$	(4	)	$	(24	)
After-tax amount recognized in AOCI at December 31,	$	108		$	251		$	(2	)	$	(17	)

Schedule of Assumptions Used [Table Text Block]

The assumptions used in accounting for the BNSF plans were as follows:

	Pension Benefits
	Year Ended		Year Ended		Year Ended
Assumptions Used to Determine Net Cost	December 31, 2018		December 31, 2017		December 31, 2016
Discount rate	3.6	%	4.1	%	4.2	%
Expected long-term rate of return on plan assets	6.6	%	6.6	%	6.6	%
Rate of compensation increase	3.6	%	3.3	%	3.8	%

	Retiree Health and Welfare Benefits
	Year Ended		Year Ended		Year Ended
Assumptions Used to Determine Net Cost	December 31, 2018		December 31, 2017		December 31, 2016
Discount rate	3.5	%	3.9	%	4.1	%
Rate of compensation increase	3.6	%	3.3	%	3.8	%

	Pension Benefits				Retiree Health and Welfare Benefits
Assumptions Used to Determine Benefit Obligations	December 31, 2018		December 31, 2017		December 31, 2018		December 31, 2017
Discount rate	4.2	%	3.6	%	4.1	%	3.5	%
Rate of compensation increase	3.5	%	3.6	%	3.5	%	3.6	%

Sensitivity analysis of impact on future net benefit cost resulting from hypothetical change in assumptions [Text Block]

The following table is an estimate of the impact on future net benefit cost that could result from hypothetical changes to the most sensitive assumptions, the discount rate and expected rate of return on plan assets:

Sensitivity Analysis
	Change in 2019 Net Benefit Cost
Hypothetical Discount Rate Change	Pension				Retiree Health and Welfare
50 basis point decrease	$	3	million	increase	$	—		decrease
50 basis point increase	$	9	million	decrease	$	1	million	increase
Hypothetical Expected Rate of Return on Plan Assets Change	Pension				Retiree Health and Welfare
50 basis point decrease	$	12	million	increase	$	—		increase
50 basis point increase	$	12	million	decrease	$	—		decrease

Schedule of Health Care Cost Trend Rates [Table Text Block]

The following table presents assumed health care cost trend rates:

	Year Ended		Year Ended		Year Ended
	December 31, 2018		December 31, 2017		December 31, 2016
Assumed health care cost trend rate for next year (participants over 65)	3.0	%	3.0	%	3.0	%
Assumed health care cost trend rate for next year (participants under 65)	6.7	%	7.0	%	7.4	%
Rate to which health care cost trend rate for participants under 65 is expected to decline and remain	4.5	%	4.5	%	4.4	%
Year that the rate reaches the ultimate trend rate	2039		2039		2039

Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]

A one percentage point change in assumed health care cost trend rates would have the following effects (in millions):

	One Percentage- Point Increase		One Percentage- Point Decrease
Effect on total service and interest cost	$	1	$	(1	)
Effect on postretirement benefit obligation	$	14	$	(12	)

Schedule of Allocation of Plan Assets [Table Text Block]

The following table summarizes the investments of BNSF’s funded pension plans as of December 31, 2018, based on the inputs used to value them (in millions):

	Total as of
Asset Category	December 31, 2018		Level 1 Inputs a		Level 2 Inputs a		Level 3 Inputs a
Cash and equivalents	$	21	$	1	$	20	$	—
Equity securitiesb	1,895		1,895		—		—
Government obligations	403		403		—		—
Other fixed maturity securities	14		—		14		—
Investment funds and other	3		3		—		—
Totalc	$	2,336	$	2,302	$	34	$	—

^a See Note 2 to the Consolidated Financial Statements under the heading “Fair Value Measurements” for a definition of each of these levels of inputs.

^b As of December 31, 2018, three equity securities each exceeded 10 percent of total plan assets. These investments represent approximately 51 percent of total plan assets.

^c Excludes less than $1 million accrued for dividend and interest receivable.

Comparative Prior Year Information

The following table summarizes the investments of BNSF’s funded pension plans as of December 31, 2017, based on the inputs used to value them (in millions):

	Total as of
Asset Category	December 31, 2017		Level 1 Inputs a		Level 2 Inputs a		Level 3 Inputs a
Cash and equivalents	$	13	$	2	$	11	$	—
Equity securitiesb	2,440		2,440		—		—
Government obligations	197		197		—		—
Other fixed maturity securities	14		—		14		—
Investment funds and other	5		5		—		—
Total c	$	2,669	$	2,644	$	25	$	—

^a See Note 2 to the Consolidated Financial Statements under the heading “Fair Value Measurements” for a definition of each of these levels of inputs.

^b As of December 31, 2017, three equity securities each exceeded 10 percent of total plan assets.  These investments represented approximately 47 percent of total plan assets.

^c Excludes less than $1 million accrued for dividend and interest receivable.

Schedule of Expected Benefit Payments Years 2018 - 2027 [Table Text Block]

The following table shows expected benefit payments from its defined benefit pension plans and expected claim payments for the retiree health and welfare plan for the next five fiscal years and the aggregate five years thereafter (in millions):

Fiscal year	Expected Pension Plan Benefit Paymentsa		Expected Retiree Health and Welfare Paymentsb
2019	$	183	$	18
2020	$	150	$	17
2021	$	144	$	17
2022	$	139	$	16
2023	$	134	$	15
2024-2028	$	633	$	67

^a Primarily consists of the BNSF Retirement Plan payments, which are made from the plan trust and do not represent an immediate cash outflow to the Company.

^b Expected payments for a portion of 2019 will be made from the plan trust and do not represent an immediate cash outflow to the Company.