Discontinued Operations and Dispositions (Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Sep. 30, 2018
Liabilities
Noncontrolling interests	$ 141	$ 149
Contracted Power Segment | Discontinued Operations, Held-for-sale or Disposed of by Sale
Assets
Cash and cash equivalents	3
Restricted cash	14
Accounts receivable, net	9
Other current assets	5
Total current assets	31
Property, equipment, land and leasehold improvements, net	606
Intangible assets, net	9
Other noncurrent assets	2
Total assets	648
Liabilities
Accounts payable and accrued expenses	7
Current portion of long-term debt	20
Other current liabilities	1
Total current liabilities	28
Long term debt, net of current portion	283
Other noncurrent liabilities	6
Total liabilities	317
Noncontrolling interests	$ 141