Commitments and Contingencies - Commitments Table (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Contractual Obligation [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 115,000,000
Operating Leases, Future Minimum Payments, Due in Two Years	100,000,000
Operating Leases, Future Minimum Payments, Due in Three Years	80,000,000
Operating Leases, Future Minimum Payments, Due in Four Years	65,000,000
Operating Leases, Future Minimum Payments, Due in Five Years	48,000,000
Operating Leases, Future Minimum Payments, Due Thereafter	794,000,000
Operating Leases, Future Minimum Payments Due	1,202,000,000
Contractual Obligation, Due in Next Twelve Months	5,738,000,000
Contractual Obligation, Due in Second Year	3,709,000,000
Contractual Obligation, Due in Third Year	1,832,000,000
Contractual Obligation, Due in Fourth Year	1,690,000,000
Contractual Obligation, Due in Fifth Year	1,407,000,000
Contractual Obligation, Due after Fifth Year	11,319,000,000
Contractual Obligation	25,695,000,000
Rent expense	118,000,000	112,000,000	101,000,000
Fuel, capacity and transmission contract commitments [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	2,525,000,000
Purchase Obligation, Due in Second Year	1,850,000,000
Purchase Obligation, Due in Third Year	1,563,000,000
Purchase Obligation, Due in Fourth Year	1,501,000,000
Purchase Obligation, Due in Fifth Year	1,268,000,000
Purchase Obligation, Due after Fifth Year	9,883,000,000
Purchase Obligation	18,590,000,000
Construction commitments [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	2,950,000,000
Purchase Obligation, Due in Second Year	1,643,000,000
Purchase Obligation, Due in Third Year	80,000,000
Purchase Obligation, Due in Fourth Year	30,000,000
Purchase Obligation, Due in Fifth Year	12,000,000
Purchase Obligation, Due after Fifth Year	85,000,000
Purchase Obligation	4,800,000,000
Maintenance, Service And Other Contracts [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	148,000,000
Purchase Obligation, Due in Second Year	116,000,000
Purchase Obligation, Due in Third Year	109,000,000
Purchase Obligation, Due in Fourth Year	94,000,000
Purchase Obligation, Due in Fifth Year	79,000,000
Purchase Obligation, Due after Fifth Year	557,000,000
Purchase Obligation	1,103,000,000
Topaz [Member]
Contractual Obligation [Line Items]
Equity funding and contribution agreement, amount committed	2,440,000,000
Equity commitment, outstanding amount	1,280,000,000
Solar Star Projects [Member]
Contractual Obligation [Line Items]
Equity funding and contribution agreement, amount committed	2,750,000,000
Equity commitment, outstanding amount	1,750,000,000
MidAmerican Funding [Member]
Contractual Obligation [Line Items]
Coal transportation costs, railroad	$ 174,000,000
Number of Construction Projects	4