Significant Accounting Policies (Financing Receivables Classified by Internal Grade of Credit Risk) (Details) $ in Millions	Sep. 30, 2026 USD ($)
Notes receivable
Year of Origination
2026	$ 50
2025	247
2024 and Prior	1,321
Total	1,618
Notes receivable \| Internal grade 1
Year of Origination
2026	47
2025	232
2024 and Prior	27
Total	306
Notes receivable \| Internal grade 1 \| DTE Electric
Year of Origination
2026	16
2025	232
2024 and Prior	25
Total	273
Notes receivable \| Internal grade 2
Year of Origination
2026	3
2025	15
2024 and Prior	1,294
Total	1,312
Net investment in leases
Year of Origination
2026	0
2025	0
2024 and Prior	35
Total	35
Net investment in leases \| Internal grade 1
Year of Origination
2026	0
2025	0
2024 and Prior	34
Total	34
Net investment in leases \| Internal grade 2
Year of Origination
2026	0
2025	0
2024 and Prior	1
Total	$ 1

Amortized cost excluding accrued interest of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-79

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant