Significant Accounting Policies (Financing Receivables Classified by Internal Grade of Credit Risk) (Details) $ in Millions	Jun. 30, 2021 USD ($)
Notes receivable
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 1
2020	86
2019 and Prior	57
Total	144
Notes receivable | DTE Electric
Financing Receivable, Credit Quality Indicator [Line Items]
Total	16
Notes receivable | Internal grade 1
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019 and Prior	24
Total	24
Notes receivable | Internal grade 1 | DTE Electric
Financing Receivable, Credit Quality Indicator [Line Items]
Total	14
Notes receivable | Internal grade 2
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1
2020	86
2019 and Prior	22
Total	109
Notes receivable | Internal grade 2 | DTE Electric
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2
Notes receivable | Internal grade 3
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019 and Prior	11
Total	11
Notes receivable | Internal grade 3 | DTE Electric
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0
Net investment in leases
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	163
2019 and Prior	40
Total	203
Net investment in leases | DTE Electric
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0
Net investment in leases | Internal grade 1
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	3
2019 and Prior	39
Total	42
Net investment in leases | Internal grade 1 | DTE Electric
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0
Net investment in leases | Internal grade 2
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	160
2019 and Prior	1
Total	161
Net investment in leases | Internal grade 2 | DTE Electric
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 0