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