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Regulatory Matters - MEC - Regulatory Liabilities (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Regulatory Liabilities [Line Items]    
Regulatory liabilities $ 2,933 $ 2,631
Removal Costs [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years [1] 27 years  
Asset Retirement Obligation Costs [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years 35 years  
Pension and other postretirement costs [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years [2] 12 years  
Unrealized gain on regulated derivative contracts [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years [2] 1 year  
MidAmerican Energy Company [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities $ 883 831
MidAmerican Energy Company [Member] | Removal Costs [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years [3] 29 years  
Regulatory liabilities [3] $ 665 653
MidAmerican Energy Company [Member] | Asset Retirement Obligation Costs [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years [4] 36 years  
Regulatory liabilities [4] $ 117 140
MidAmerican Energy Company [Member] | Transmission MVP CWIP Return [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years [5] 56 years  
Regulatory liabilities [5] $ 35 19
MidAmerican Energy Company [Member] | Regulatory revenue sharing arrangement [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years [6] 1 year  
Regulatory liabilities [6] $ 30 0
MidAmerican Energy Company [Member] | Pension and other postretirement costs [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years [7] 11 years  
Regulatory liabilities [7] $ 12 0
MidAmerican Energy Company [Member] | Unrealized gain on regulated derivative contracts [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years 1 year  
Regulatory liabilities $ 6 0
MidAmerican Energy Company [Member] | Other Regulatory Assets (Liabilities) [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liability amortization period years Various  
Regulatory liabilities $ 18 $ 19
[1] Amounts represent estimated costs, as accrued through depreciation rates and exclusive of ARO liabilities, of removing regulated property, plant and equipment in accordance with accepted regulatory practices. Amounts are deducted from rate base or otherwise accrue a carrying cost.
[2] Represents amounts not yet recognized as a component of net periodic benefit cost that are to be returned to customers in future periods when recognized.ALP General Tariff Application ("GTA")In November 2014, ALP filed a GTA requesting the Alberta Utilities Commission ("AUC") to approve revenue requirements of C$811 million for 2015 and C$1.0 billion for 2016, primarily due to continued investment in capital projects as directed by the Alberta Electric System Operator. ALP amended the GTA in June 2015 to propose transmission tariff relief measures for customers and modifications to its capital structure. ALP also amended and updated the GTA in October 2015, reducing the requested revenue requirements to C$672 million for 2015 and C$704 million for 2016. In May 2016, the AUC issued its decision pertaining to the 2015-2016 GTA. ALP filed its 2015-2016 GTA compliance filing in July 2016 to comply with the AUC's decision.The compliance filing requested the AUC to approve revenue requirements of C$599 million for 2015 and C$685 million for 2016. The decreased revenue requirements requested in the compliance filing, as compared to the 2015-2016 GTA filing updated in October 2015, were primarily due to the AUC approval of ALP's proposed immediate tariff relief of C$415 million for customers for 2015 and 2016, through (i) the discontinuance of construction work-in-progress ("CWIP") in rate base and the return to allowance for funds used during construction ("AFUDC") accounting effective January 1, 2015, resulting in a C$82 million reduction of revenue requirement and the refund of C$277 million previously collected as CWIP in rate base as part of ALP's transmission tariffs during 2011-2014 less related returns of C$12 million and (ii) a change to the flow through method for calculating income taxes for 2016, resulting in further tariff relief of C$68 million.Operating revenue for the year ended December 31, 2016, included a one-time reduction of $200 million from the 2015-2016 GTA decision received in May 2016 at ALP. The 2015-2016 GTA decision required ALP to refund $200 million to customers in 2016 through reduced monthly billings for the change from receiving cash during construction for the return on CWIP in rate base to recording allowance for borrowed and equity funds used during construction related to construction expenditures during the 2011 to 2014 time period. This amount is offset with higher capitalized interest and allowance for equity funds in the Consolidated Statements of Operations. In addition, the decision required ALP to change to the flow through method of recognizing income tax expense effective January 1, 2016. This change reduced operating revenue by $45 million for the year ended December 31, 2016, with offsetting impacts to income tax expense in the Consolidated Statements of Operations.
[3] (1)Amounts represent estimated costs, as accrued through depreciation rates and exclusive of ARO liabilities, of removing utility plant in accordance with accepted regulatory practices. Amounts are deducted from rate base or otherwise accrue a carrying cost.
[4] (2)Amount predominantly represents the excess of nuclear decommission trust assets over the related asset retirement obligation. Refer to Note 12 for a discussion of asset retirement obligations.
[5] (3)Represents AFUDC accrued on transmission MVPs that is deducted from rate base as a result of the inclusion of related construction work-in-progress in rate base.
[6] (4)Represents current-year accruals under a regulatory arrangement in Iowa in which equity returns exceeding specified thresholds reduce utility plant upon final determination.
[7] (5)Represents amounts not yet recognized as a component of net periodic benefit cost that are to be returned to customers in future periods when recognized.