Pension plans - Projected benefit obligation, plan assets and net funded status (Detail) - Pension Plans, Defined Benefit [Member] - USD ($)
$ in Millions |
12 Months Ended |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
| Benefit obligations |
|
|
|
| Accumulated benefit obligation end of year |
$ 15,886
|
$ 17,524
|
|
| PBO beginning of year |
18,824
|
17,750
|
|
| Service cost |
271
|
273
|
$ 282
|
| Interest cost |
593
|
635
|
691
|
| Benefits paid |
(841)
|
(897)
|
|
| Settlements |
(434)
|
(241)
|
|
| Actuarial (gains) or losses and other |
(1,491)
|
1,304
|
|
| PBO end of year |
16,922
|
18,824
|
17,750
|
| Plan assets |
|
|
|
| Plan assets beginning of year |
17,014
|
15,397
|
|
| Employer contributions |
593
|
281
|
|
| Benefits paid |
(841)
|
(897)
|
|
| Actual return on plan assets |
(1,140)
|
2,136
|
|
| Settlements |
(456)
|
(235)
|
|
| Other |
(211)
|
332
|
|
| Plan assets end of year |
14,959
|
17,014
|
15,397
|
| Funded status - net liability |
1,963
|
1,810
|
|
| Berkshire Hathaway Energy [Member] |
|
|
|
| Benefit obligations |
|
|
|
| Accumulated benefit obligation end of year |
4,346
|
4,920
|
|
| PBO beginning of year |
5,207
|
5,077
|
|
| Service cost |
40
|
47
|
|
| Interest cost |
161
|
174
|
|
| Benefits paid |
(208)
|
(271)
|
|
| Settlements |
(301)
|
(146)
|
|
| Actuarial (gains) or losses and other |
(348)
|
326
|
|
| PBO end of year |
4,551
|
5,207
|
5,077
|
| Plan assets |
|
|
|
| Plan assets beginning of year |
5,129
|
4,694
|
|
| Employer contributions |
98
|
122
|
|
| Benefits paid |
(208)
|
(271)
|
|
| Actual return on plan assets |
(191)
|
535
|
|
| Settlements |
(324)
|
(159)
|
|
| Other |
(119)
|
208
|
|
| Plan assets end of year |
4,385
|
5,129
|
4,694
|
| Funded status - net liability |
166
|
78
|
|
| All Other [Member] |
|
|
|
| Benefit obligations |
|
|
|
| Accumulated benefit obligation end of year |
11,540
|
12,604
|
|
| PBO beginning of year |
13,617
|
12,673
|
|
| Service cost |
231
|
226
|
|
| Interest cost |
432
|
461
|
|
| Benefits paid |
(633)
|
(626)
|
|
| Settlements |
(133)
|
(95)
|
|
| Actuarial (gains) or losses and other |
(1,143)
|
978
|
|
| PBO end of year |
12,371
|
13,617
|
12,673
|
| Plan assets |
|
|
|
| Plan assets beginning of year |
11,885
|
10,703
|
|
| Employer contributions |
495
|
159
|
|
| Benefits paid |
(633)
|
(626)
|
|
| Actual return on plan assets |
(949)
|
1,601
|
|
| Settlements |
(132)
|
(76)
|
|
| Other |
(92)
|
124
|
|
| Plan assets end of year |
10,574
|
11,885
|
$ 10,703
|
| Funded status - net liability |
$ 1,797
|
$ 1,732
|
|