Long-term and Short-term Debt (Credit Facilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Collateral financing arrangement	$ 993	$ 1,060
General Credit Facility Three [Member]
Debt Instrument [Line Items]
Borrowers	MetLife, Inc. and MetLife Funding, Inc.
Expiration	Dec. 20, 2021
Line of Credit Facility, Maximum Borrowing Capacity	$ 3,000
Letters of Credit Issued	746
Collateral financing arrangement	0
Unused Commitments	$ 2,254
Standby Letters of Credit [Member] | General Credit Facility Three [Member]
Debt Instrument [Line Items]
Expiration	Dec. 20, 2022