Pension plans - Projected benefit obligation, plan assets and net funded status (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
BHE Pension Plan [Member]
Benefit obligations
Accumulated benefit obligation end of year	$ 4,787	$ 4,797
PBO beginning of year	5,076	5,398
Service cost	49	57
Interest cost	198	200
Benefits paid	(309)	(316)
Actuarial (gains) or losses and other	63	(263)
PBO end of year	5,077	5,076	$ 5,398
Plan assets
Plan assets beginning of year	4,765	5,086
Employer contributions	133	90
Benefits paid	(309)	(316)
Actual return on plan assets	512	31
Other	(407)	(126)
Plan assets end of year	4,694	4,765	5,086
Funded status - net liability	383	311
All Other Pension Plans [Member]
Benefit obligations
Accumulated benefit obligation end of year	11,912	9,264
PBO beginning of year	10,183	10,489
Service cost	233	209
Interest cost	493	391
Benefits paid	(705)	(518)
Business acquisitions	2,684	165
Actuarial (gains) or losses and other	(215)	(553)
PBO end of year	12,673	10,183	10,489
Plan assets
Plan assets beginning of year	8,066	8,280
Employer contributions	214	116
Benefits paid	(705)	(518)
Actual return on plan assets	1,083	80
Business acquisitions	2,314	167
Other	(269)	(59)
Plan assets end of year	10,703	8,066	8,280
Funded status - net liability	1,970	2,117
Pension Plans, Defined Benefit [Member]
Benefit obligations
Accumulated benefit obligation end of year	16,699	14,061
PBO beginning of year	15,259	15,887
Service cost	282	266	230
Interest cost	691	591	629
Benefits paid	(1,014)	(834)
Business acquisitions	2,684	165
Actuarial (gains) or losses and other	(152)	(816)
PBO end of year	17,750	15,259	15,887
Plan assets
Plan assets beginning of year	12,831	13,366
Employer contributions	347	206
Benefits paid	(1,014)	(834)
Actual return on plan assets	1,595	111
Business acquisitions	2,314	167
Other	(676)	(185)
Plan assets end of year	15,397	12,831	$ 13,366
Funded status - net liability	$ 2,353	$ 2,428