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, 2019	Dec. 31, 2018	Dec. 31, 2017
Benefit obligations
Accumulated benefit obligation end of year	$ 17,542	$ 15,886
PBO beginning of year	16,922	18,824
Service cost	224	271	$ 273
Interest cost	618	593	635
Benefits paid	(1,033)	(841)
Settlements	(167)	(434)
Actuarial (gains) or losses and other	2,142	(1,491)
PBO end of year	18,706	16,922	18,824
Plan assets
Plan assets beginning of year	14,959	17,014
Employer contributions	199	593
Benefits paid	(1,033)	(841)
Actual return on plan assets	2,414	(1,140)
Settlements	(167)	(456)
Other	124	(211)
Plan assets end of year	16,496	14,959	17,014
Funded status – net liability	2,210	1,963
Berkshire Hathaway Energy [Member]
Benefit obligations
Accumulated benefit obligation end of year	4,653	4,346
PBO beginning of year	4,551	5,207
Service cost	32	40
Interest cost	161	161
Benefits paid	(257)	(208)
Settlements	(121)	(301)
Actuarial (gains) or losses and other	532	(348)
PBO end of year	4,898	4,551	5,207
Plan assets
Plan assets beginning of year	4,385	5,129
Employer contributions	68	98
Benefits paid	(257)	(208)
Actual return on plan assets	650	(191)
Settlements	(121)	(324)
Other	83	(119)
Plan assets end of year	4,808	4,385	5,129
Funded status – net liability	90	166
All Other [Member]
Benefit obligations
Accumulated benefit obligation end of year	12,889	11,540
PBO beginning of year	12,371	13,617
Service cost	192	231
Interest cost	457	432
Benefits paid	(776)	(633)
Settlements	(46)	(133)
Actuarial (gains) or losses and other	1,610	(1,143)
PBO end of year	13,808	12,371	13,617
Plan assets
Plan assets beginning of year	10,574	11,885
Employer contributions	131	495
Benefits paid	(776)	(633)
Actual return on plan assets	1,764	(949)
Settlements	(46)	(132)
Other	41	(92)
Plan assets end of year	11,688	10,574	$ 11,885
Funded status – net liability	$ 2,120	$ 1,797