XML 161 R128.htm IDEA: XBRL DOCUMENT v3.10.0.1
Schedule I - Condensed Financial Information of Registrant (Narrative) (Details) - USD ($)
$ in Millions
Dec. 31, 2018
Jul. 31, 2018
CMS Energy    
Condensed Financial Statements, Captions [Line Items]    
Maximum potential obligation $ 433  
CMS Energy Note Payable    
Condensed Financial Statements, Captions [Line Items]    
Notes payable   $ 146
Interest rate   4.10%
CMS Energy Note Payable | Subsidiaries    
Condensed Financial Statements, Captions [Line Items]    
Notes payable   $ 124