Exit Activities and Discontinued Operations - Assets and Liabilities of Discontinued Operation (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Current
Total current assets	$ 19	$ 429
Non‑current
Total non‑current assets	0	2,680
Current
Total current liabilities	0	953
Non‑current
Total non‑current liabilities	0	1,894
Discontinued Operations, Held-for-sale
Current
Cash and cash equivalents	$ 0	136
Discontinued Operations, Held-for-sale | EnerBank
Current
Cash and cash equivalents		136
Accounts receivable and other current assets		18
Notes receivable, less allowance of $32		275
Total current assets		429
Non‑current
Plant, property, and equipment, net		22
Notes receivable, less allowance of $91		2,612
Other non‑current assets		46
Total non‑current assets		2,680
Total assets		3,109
Current
Current portion of long-term debt		915
Accounts payable and other current liabilities		38
Total current liabilities		953
Non‑current
Long-term debt		1,890
Other non‑current liabilities		4
Total non‑current liabilities		1,894
Total liabilities		2,847
Notes receivable, allowance, current		32
Notes receivable, allowance, noncurrent		$ 91