Long-term and Short-term Debt Long-term and Short-term Debt (Narrative - Line of Credit) (Details) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2037	Dec. 01, 2037	Dec. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Jun. 30, 2018	Mar. 31, 2018	Nov. 01, 2017	Jul. 21, 2017	Jun. 30, 2017	Dec. 11, 2015
Committed Credit Facility Six [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Dec. 31, 2037
Line of Credit Facility, Remaining Borrowing Capacity		$ 542,000,000
Line of Credit Facility, Maximum Borrowing Capacity		2,896,000,000
Line of Credit Facility, Current Borrowing Capacity		$ 2,600,000,000
Committed Credit Facility Four [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Jun. 20, 2018
Line of Credit Facility, Remaining Borrowing Capacity		$ 0
Line of Credit Facility, Maximum Borrowing Capacity		$ 395,000,000
General Credit Facility Three [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Dec. 20, 2021
Line of Credit Facility, Remaining Borrowing Capacity		$ 2,870,000,000
Line of Credit Facility, Maximum Borrowing Capacity		$ 3,000,000,000
Committed Credit Facility Three [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Dec. 28, 2024
Line of Credit Facility, Remaining Borrowing Capacity		$ 20,000,000
Line of Credit Facility, Maximum Borrowing Capacity		400,000,000
Committed Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity		562,000,000
Line of Credit Facility, Maximum Borrowing Capacity		3,691,000,000
Other Notes MPEH [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		75,000,000
Amendment [Member] | Other Notes MPEH [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity														$ 75,000,000			$ 100,000,000
Committed Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		3,700,000,000
Line of Credit Facility, Commitment Fee Amount		21,000,000	$ 27,000,000	$ 29,000,000
General Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Commitment Fee Amount		13,000,000	15,000,000	13,000,000
Brighthouse Financial, Inc [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 3,000,000,000														$ 600,000,000	$ 536,000,000
Line of Credit Facility, Current Borrowing Capacity															$ 500,000,000
Brighthouse Financial, Inc [Member] | Committed Credit Facility Six [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		2,900,000,000
Brighthouse Financial, Inc [Member] | Committed Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Commitment Fee Amount	$ 257,000,000	$ 305,000,000	$ 69,000,000	$ 61,000,000
Scenario, Forecast [Member] | Committed Credit Facility Six [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 0	$ 2,000,000,000
Scenario, Forecast [Member] | Committed Credit Facility Four [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity												$ 0	$ 200,000,000
Scenario, Forecast [Member] | Committed Credit Facility Three [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity							$ 0	$ 260,000,000	$ 310,000,000	$ 360,000,000	$ 380,000,000