Significant Accounting Policies (Financing Receivables Classified by Internal Grade of Credit Risk) (Details) $ in Millions	Sep. 30, 2020 USD ($)
Notes receivable
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 60
2019	37
2018 and prior	15
Total	112
Notes receivable | Internal grade 1
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	18
2018 and prior	9
Total	27
Notes receivable | Internal grade 2
Financing Receivable, Credit Quality Indicator [Line Items]
2020	60
2019	19
2018 and prior	6
Total	85
Net investment in leases
Financing Receivable, Credit Quality Indicator [Line Items]
2020	140
2019	0
2018 and prior	41
Total	181
Net investment in leases | Internal grade 1
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8
2019	0
2018 and prior	40
Total	48
Net investment in leases | Internal grade 2
Financing Receivable, Credit Quality Indicator [Line Items]
2020	132
2019	0
2018 and prior	1
Total	133
DTE Electric | Notes receivable
Financing Receivable, Credit Quality Indicator [Line Items]
Total	18
DTE Electric | Notes receivable | Internal grade 1
Financing Receivable, Credit Quality Indicator [Line Items]
Total	18
DTE Electric | Notes receivable | Internal grade 2
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0
DTE Electric | Net investment in leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0
DTE Electric | Net investment in leases | Internal grade 1
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0
DTE Electric | Net investment in leases | Internal grade 2
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 0