Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Schedule of Other Income

The following is a summary of DTE Energy's Other income:

	2017		2016		2015
	(In millions)
Equity earnings of equity method investees	$	102	$	68	$	66
Income from REF entities	77		75		83
Gains from trading securities	26		15		1
Allowance for equity funds used during construction	23		21		21
Contract services	19		21		27
Other	21		7		11
	$	268	$	207	$	209

The following is a summary of DTE Electric's Other income:

	2017		2016		2015
	(In millions)
Gains from trading securities allocated from DTE Energy	$	26	$	15	$	1
Contract services	21		20		27
Allowance for equity funds used during construction	18		18		20
Equity earnings of equity method investees	1		2		2
Other	11		6		10
	$	77	$	61	$	60

Schedule of Accumulated Other Comprehensive Income (Loss)

The following table summarizes the changes in DTE Energy's Accumulated other comprehensive income (loss) by component^(a) for the years ended December 31, 2017 and 2016:

	Net Unrealized Gain (Loss) on Derivatives			Net Unrealized Gain (Loss) on Investments			Benefit Obligations(b)			Foreign Currency Translation			Total
	(In millions)
Balance, December 31, 2015	$	(4	)	$	(4	)	$	(131	)	$	(6	)	$	(145	)
Other comprehensive loss before reclassifications	—			—			(3		)	—			(3		)
Amounts reclassified from Accumulated other comprehensive income	—			1			14			—			15
Net current-period Other comprehensive income	—			1			11			—			12
Balance, December 31, 2016	$	(4	)	$	(3	)	$	(120	)	$	(6	)	$	(133	)
Other comprehensive income (loss) before reclassifications	—			1			(3		)	1			(1		)
Amounts reclassified from Accumulated other comprehensive income	1			—			13			—			14
Net current-period Other comprehensive income	1			1			10			1			13
Balance, December 31, 2017	$	(3	)	$	(2	)	$	(110	)	$	(5	)	$	(120	)

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(a) All amounts are net of tax, except for Foreign currency translation.

(b) The amounts reclassified from Accumulated other comprehensive income (loss) are included in the computation of the net periodic pension and other postretirement benefit costs (see Note 20 to the Consolidated Financial Statements "Retirement Benefits and Trusteed Assets").

Schedule of Finite-Lived Intangible Assets by Major Class

The Registrants have certain Intangible assets as shown below:

		December 31, 2017							December 31, 2016
	Useful Lives	Gross Carrying Value		Accumulated Amortization			Net Carrying Value		Gross Carrying Value		Accumulated Amortization			Net Carrying Value
		(In millions)
Intangible assets subject to amortization
Customer relationships(a)	40 years(b)	$	770	$	(24	)	$	746	$	770	$	(5	)	$	765
Contract intangibles	6 to 26 years	168		(72		)	96		111		(65		)	46
		938		(96		)	842		881		(70		)	811
DTE Electric renewable energy credits	(c)	24		—			24		30		—			30
DTE Electric emission allowances	(c)	1		—			1		1		—			1
		25		—			25		31		—			31
Long-term intangible assets
DTE Electric		$	25	$	—		$	25	$	31	$	—		$	31
DTE Energy		$	963	$	(96	)	$	867	$	912	$	(70	)	$	842

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(a) In October 2016, DTE Energy acquired midstream natural gas assets that are part of the Gas Storage and Pipelines segment. The intangible assets recorded as a result of the acquisition pertain to existing customer relationships. See Note 4 to the Consolidated Financial Statements, "Acquisitions and Exit Activities," for additional information.

(b) The useful life of the customer relationship intangible assets is based on the number of years in which the assets are expected to economically contribute to the business. The expected economic benefit incorporates existing customer contracts and expected renewal rates based on the estimated volume and production lives of gas resources in the region.

(c) Emission allowances and renewable energy credits are charged to expense, using average cost, as the allowances and credits are consumed in the operation of the business.

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense

The following table summarizes DTE Energy's estimated customer relationship and contract intangible amortization expense expected to be recognized during each year through 2022:

	2018		2019		2020		2021		2022
	(In millions)
Estimated amortization expense	$	26	$	26	$	25	$	25	$	25

Schedule Of Accounting Policies

See the following notes for other accounting policies impacting the Registrants’ Consolidated Financial Statements:

Note	Title
8	Asset Retirement Obligations
9	Regulatory Matters
10	Income Taxes
12	Fair Value
13	Financial and Other Derivative Instruments
20	Retirement Benefits and Trusteed Assets
21	Stock-Based Compensation