Long-Term Debt and Credit Facilities - Revolving Letters of Credit (Details) $ in Millions	Jun. 30, 2025 USD ($)
Long-term Debt and Credit Facilities
Letters of credit outstanding	$ 234
Facility Maintained By a Subsidiary
Long-term Debt and Credit Facilities
Letters of credit outstanding	3
Letter of Credit | Uncommitted Letter of Credit Facility
Long-term Debt and Credit Facilities
Maximum borrowing capacity	225
Revolving Credit Facility
Long-term Debt and Credit Facilities
Letters of credit outstanding	$ 231