Dispositions - Separation of Brighthouse - Ongoing Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jul. 21, 2017	Jun. 30, 2017	Apr. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Intra-Entity Amounts, Discontinued Operation after Disposal, Revenue	$ 61	$ 48
Brighthouse Financial, Inc
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue from Related Parties	57
Line of Credit Facility, Maximum Borrowing Capacity			$ 600	$ 536	$ 3,000
Committed Credit Facility Six [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	2,896
Letters of Credit Outstanding, Amount	2,420
Committed Credit Facility Six [Member] | Brighthouse Financial, Inc
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	2,900
Letters of Credit Outstanding, Amount	$ 2,400	$ 2,400