Significant Accounting Policies (Financing Receivables Classified by Internal Grade of Credit Risk) (Details) $ in Millions	Mar. 31, 2021 USD ($)
Notes receivable
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 1
2020	64
2019 and Prior	75
Total	140
Notes receivable | Internal grade 1
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019 and Prior	23
Total	23
Notes receivable | Internal grade 2
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1
2020	64
2019 and Prior	52
Total	117
Net investment in leases
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	165
2019 and Prior	40
Total	205
Net investment in leases | Internal grade 1
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	4
2019 and Prior	39
Total	43
Net investment in leases | Internal grade 2
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	161
2019 and Prior	1
Total	162
DTE Electric | Notes receivable
Financing Receivable, Credit Quality Indicator [Line Items]
Total	16
DTE Electric | Notes receivable | Internal grade 1
Financing Receivable, Credit Quality Indicator [Line Items]
Total	14
DTE Electric | Notes receivable | Internal grade 2
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2
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