Litigation, Contractual Commitments, and Contingent Liabilities - Exit Costs Accrual Composition (Details) - Discontinued operations, disposed of by means other than sale, abandonment - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, including discontinued operation, other liabilities	$ 77	$ 144
Future obligations under land lease agreements
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, including discontinued operation, other liabilities	0	43
Iowa greyhound pari-mutuel racing fund
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, including discontinued operation, other liabilities	25	33
Permanent closure of Alea Leeds
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, including discontinued operation, other liabilities	0	10
Unbundling of electric service provided by NV Energy
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, including discontinued operation, other liabilities	$ 52	$ 58