Pension plans- Projected benefit obligation, plan assets and net funded status (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
MidAmerican Pension Plan [Member]
Benefit Obligations
Accumulated benefit obligation at end of year	$ 4,664	$ 4,037
PBO at beginning of year	4,284	3,863
Service cost	46	44
Interest cost	172	183
Benefits paid	(275)	(219)
Business acquisitions	823
Actuarial (gains) or losses and other	(44)	413
PBO at end of year	5,006	4,284
Plan Assets
Plan assets at beginning of year	3,651	3,245
Employer contributions	150	193
Benefits paid	(275)	(219)
Actual return on plan assets	497	341
Business acquisitions	818
Other	47	91
Plan assets at end of year	4,888	3,651
Net funded status - net liability	118	633
All Other Pension Plans [Member]
Benefit Obligations
Accumulated benefit obligation at end of year	8,101	8,878
PBO at beginning of year	9,789	9,129
Service cost	208	203
Interest cost	375	400
Benefits paid	(505)	(660)
Business acquisitions		8
Actuarial (gains) or losses and other	(975)	709
PBO at end of year	8,892	9,789
Plan Assets
Plan assets at beginning of year	6,785	5,905
Employer contributions	274	456
Benefits paid	(505)	(660)
Actual return on plan assets	1,849	1,088
Business acquisitions		6
Other	(14)	(10)
Plan assets at end of year	8,389	6,785
Net funded status - net liability	503	3,004
Pension Plans, Defined Benefit [Member]
Benefit Obligations
Accumulated benefit obligation at end of year	12,765	12,915
PBO at beginning of year	14,073	12,992
Service cost	254	247	191
Interest cost	547	583	568
Benefits paid	(780)	(879)
Business acquisitions	823	8
Actuarial (gains) or losses and other	(1,019)	1,122
PBO at end of year	13,898	14,073	12,992
Plan Assets
Plan assets at beginning of year	10,436	9,150
Employer contributions	424	649
Benefits paid	(780)	(879)
Actual return on plan assets	2,346	1,429
Business acquisitions	818	6
Other	33	81
Plan assets at end of year	13,277	10,436	9,150
Net funded status - net liability	$ 621	$ 3,637