Regulatory Matters	6 Months Ended
Jun. 30, 2018
Public Utilities, General Disclosures [Abstract]
Regulatory Matters	REGULATORY MATTERS 2017 Electric Rate Case Filing DTE Electric filed a rate case with the MPSC on April 19, 2017 requesting an increase in base rates of $231 million based on a projected twelve-month period ending October 31, 2018. On November 1, 2017, DTE Electric self-implemented a base rate increase of $125 million. On April 18, 2018, the MPSC issued an order approving an annual revenue increase of $65.2 million for service rendered on or after May 1, 2018. The MPSC authorized a return on equity of 10.0%. On June 28, 2018, the MPSC issued an order on a rehearing granting in part and denying in part, petitions for rehearings of DTE Electric and other intervenors. As a result, the approved addition to base rates increased from $65.2 million to $74.4 million. DTE Electric has recorded a refund liability of $25 million, representing the total estimated refund due to customers, inclusive of interest, at June 30, 2018. In August 2018, DTE Electric will file to refund its customers based on their pro rata share of the revenue collected through the self-implementation surcharge in effect from November 1, 2017 to May 1, 2018. 2018 Electric Rate Case Filing DTE Electric filed a rate case with the MPSC on July 6, 2018 requesting an increase in base rates of $328 million based on a projected twelve-month period ending April 30, 2020. The requested increase in base rates is primarily due to an increase in net plant resulting from infrastructure investments, depreciation expense, as requested in the 2016 DTE Main Electric Depreciation Case Filing, and reliability improvement projects. The rate filing also requests an increase in return on equity from 10.0% to 10.5% and includes projected changes in sales, operation and maintenance expenses, and working capital. In addition, the rate filing requests an Infrastructure Recovery Mechanism to recover the incremental revenue requirement associated with certain distribution, fossil generation, and nuclear generation capital expenditures through 2022. Finally, as noted in the 2017 Tax Reform section below, DTE Electric addressed Calculation C in this filing. A final MPSC order in this case is expected by May 2019. Certificate of Necessity On July 31, 2017, DTE Electric filed a request for authority to build a 1,100 megawatt natural gas fueled combined cycle generation facility at DTE Electric's Belle River Power Plant. DTE Electric requested the MPSC to issue three CONs for the following: (1) power supplied by the proposed project is needed, (2) the size, fuel type, and other design characteristics of the proposed project represent the most reasonable and prudent means of meeting the power need, and (3) the estimated capital costs of $989 million for the proposed project will be recoverable in rates from DTE Electric's customers. The MPSC issued an order on April 27, 2018 approving DTE Electric's request for the three CONs with recoverable amounts through rates up to $951.8 million. 2017 Gas Rate Case Filing DTE Gas filed a rate case with the MPSC on November 22, 2017 requesting an increase in base rates of $85.1 million based on a projected twelve-month period ending September 30, 2019. The requested increase in base rates is primarily due to an increase in net plant. The rate filing also requests an increase in return on equity from 10.1% to 10.5% and includes projected changes in sales, operations and maintenance expenses, and working capital. On May 24, 2018, DTE Gas reduced its initial requested increase in base rates to $38.1 million, primarily due to the effects of the TCJA on the original request. To mitigate the impact to its customers resulting from ASU No. 2017-07, Compensation — Retirement Benefits (Topic 715), DTE Gas suggested regulatory accounting treatment, consistent with the methodology approved by the MPSC in the 2017 DTE Electric Rate Case order. As such, beginning January 1, 2018, pension and postretirement cost components previously included as capital overhead are being deferred. For further discussion of ASU No. 2017-07, see Note 3 to the Consolidated Financial Statements, "New Accounting Pronouncements." A final MPSC order in this case is expected by September 2018. 2017 Tax Reform On December 27, 2017, the MPSC issued an order to consider changes in the rates of all Michigan rate-regulated utilities to reflect the effects of the federal TCJA. On January 19, 2018, DTE Electric and DTE Gas filed information with the MPSC regarding the potential change in revenue requirements due to the TCJA effective January 1, 2018, and outlined their recommended method to flow the current and deferred tax benefits of those impacts to ratepayers. On February 22, 2018, the MPSC issued an order in this case requiring utilities, including DTE Electric and DTE Gas, to follow a 3-step approach of credits and calculations. The first step is to establish Credit A, through contested cases. Credit A is a going-forward tax credit to reflect the reduction of the corporate tax rate from 35% to 21%. DTE Gas submitted its Credit A filing on March 28, 2018, reflecting a reduction in revenues of $38.2 million. The MPSC approved the $38.2 million reduction on May 30, 2018, to be effective July 1, 2018. DTE Electric filed its Credit A application on May 18, 2018, reflecting a reduction in revenues of $157 million. On July 24, 2018, the MPSC issued an order approving a settlement in DTE Electric's Credit A filing reflecting a reduction in revenues of $157 million. Rates reflecting this reduction will be effective August 1, 2018. The second step is to establish Credit B, through contested cases. Credit B is a backward-looking tax credit to reflect the reduction of the corporate rate of 35% to 21%, for the period January 1, 2018 through the date Credit A is established. The Credit B filing is required within sixty days after Credit A is implemented. For Credit B, DTE Electric and DTE Gas have been deferring the impact of the reduction to the corporate tax rate since January 1, 2018. The third step is to perform Calculation C, through contested cases. Calculation C will address all remaining issues relative to the new tax law, which is primarily the remeasurement of deferred taxes and how the amounts deferred as Regulatory liabilities will flow to ratepayers. DTE Gas is required to file Calculation C no later than October 1, 2018. DTE Electric addressed Calculation C in its general rate case filed July 6, 2018.

REGULATORY MATTERS

2017 Electric Rate Case Filing

DTE Electric filed a rate case with the MPSC on April 19, 2017 requesting an increase in base rates of $231 million based on a projected twelve-month period ending October 31, 2018. On November 1, 2017, DTE Electric self-implemented a base rate increase of $125 million. On April 18, 2018, the MPSC issued an order approving an annual revenue increase of $65.2 million for service rendered on or after May 1, 2018. The MPSC authorized a return on equity of 10.0%. On June 28, 2018, the MPSC issued an order on a rehearing granting in part and denying in part, petitions for rehearings of DTE Electric and other intervenors. As a result, the approved addition to base rates increased from $65.2 million to $74.4 million. DTE Electric has recorded a refund liability of $25 million, representing the total estimated refund due to customers, inclusive of interest, at June 30, 2018. In August 2018, DTE Electric will file to refund its customers based on their pro rata share of the revenue collected through the self-implementation surcharge in effect from November 1, 2017 to May 1, 2018.

2018 Electric Rate Case Filing

DTE Electric filed a rate case with the MPSC on July 6, 2018 requesting an increase in base rates of $328 million based on a projected twelve-month period ending April 30, 2020. The requested increase in base rates is primarily due to an increase in net plant resulting from infrastructure investments, depreciation expense, as requested in the 2016 DTE Main Electric Depreciation Case Filing, and reliability improvement projects. The rate filing also requests an increase in return on equity from 10.0% to 10.5% and includes projected changes in sales, operation and maintenance expenses, and working capital. In addition, the rate filing requests an Infrastructure Recovery Mechanism to recover the incremental revenue requirement associated with certain distribution, fossil generation, and nuclear generation capital expenditures through 2022. Finally, as noted in the 2017 Tax Reform section below, DTE Electric addressed Calculation C in this filing. A final MPSC order in this case is expected by May 2019.

Certificate of Necessity

On July 31, 2017, DTE Electric filed a request for authority to build a 1,100 megawatt natural gas fueled combined cycle generation facility at DTE Electric's Belle River Power Plant. DTE Electric requested the MPSC to issue three CONs for the following: (1) power supplied by the proposed project is needed, (2) the size, fuel type, and other design characteristics of the proposed project represent the most reasonable and prudent means of meeting the power need, and (3) the estimated capital costs of $989 million for the proposed project will be recoverable in rates from DTE Electric's customers. The MPSC issued an order on April 27, 2018 approving DTE Electric's request for the three CONs with recoverable amounts through rates up to $951.8 million.

2017 Gas Rate Case Filing

DTE Gas filed a rate case with the MPSC on November 22, 2017 requesting an increase in base rates of $85.1 million based on a projected twelve-month period ending September 30, 2019. The requested increase in base rates is primarily due to an increase in net plant. The rate filing also requests an increase in return on equity from 10.1% to 10.5% and includes projected changes in sales, operations and maintenance expenses, and working capital. On May 24, 2018, DTE Gas reduced its initial requested increase in base rates to $38.1 million, primarily due to the effects of the TCJA on the original request. To mitigate the impact to its customers resulting from ASU No. 2017-07, Compensation — Retirement Benefits (Topic 715), DTE Gas suggested regulatory accounting treatment, consistent with the methodology approved by the MPSC in the 2017 DTE Electric Rate Case order. As such, beginning January 1, 2018, pension and postretirement cost components previously included as capital overhead are being deferred. For further discussion of ASU No. 2017-07, see Note 3 to the Consolidated Financial Statements, "New Accounting Pronouncements." A final MPSC order in this case is expected by September 2018.

2017 Tax Reform

On December 27, 2017, the MPSC issued an order to consider changes in the rates of all Michigan rate-regulated utilities to reflect the effects of the federal TCJA. On January 19, 2018, DTE Electric and DTE Gas filed information with the MPSC regarding the potential change in revenue requirements due to the TCJA effective January 1, 2018, and outlined their recommended method to flow the current and deferred tax benefits of those impacts to ratepayers.

On February 22, 2018, the MPSC issued an order in this case requiring utilities, including DTE Electric and DTE Gas, to follow a 3-step approach of credits and calculations. The first step is to establish Credit A, through contested cases. Credit A is a going-forward tax credit to reflect the reduction of the corporate tax rate from 35% to 21%. DTE Gas submitted its Credit A filing on March 28, 2018, reflecting a reduction in revenues of $38.2 million. The MPSC approved the $38.2 million reduction on May 30, 2018, to be effective July 1, 2018. DTE Electric filed its Credit A application on May 18, 2018, reflecting a reduction in revenues of $157 million. On July 24, 2018, the MPSC issued an order approving a settlement in DTE Electric's Credit A filing reflecting a reduction in revenues of $157 million. Rates reflecting this reduction will be effective August 1, 2018. The second step is to establish Credit B, through contested cases. Credit B is a backward-looking tax credit to reflect the reduction of the corporate rate of 35% to 21%, for the period January 1, 2018 through the date Credit A is established. The Credit B filing is required within sixty days after Credit A is implemented. For Credit B, DTE Electric and DTE Gas have been deferring the impact of the reduction to the corporate tax rate since January 1, 2018. The third step is to perform Calculation C, through contested cases. Calculation C will address all remaining issues relative to the new tax law, which is primarily the remeasurement of deferred taxes and how the amounts deferred as Regulatory liabilities will flow to ratepayers. DTE Gas is required to file Calculation C no later than October 1, 2018. DTE Electric addressed Calculation C in its general rate case filed July 6, 2018.