Insurance (Insurance Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Insurance Liabilities [Line Items]
Insurance liabilities comprised of future policy benefits, policyholder account balances and other policy-related balances	$ 376,007	$ 352,524
U.S.
Insurance Liabilities [Line Items]
Insurance liabilities comprised of future policy benefits, policyholder account balances and other policy-related balances	136,065	129,117
Asia
Insurance Liabilities [Line Items]
Insurance liabilities comprised of future policy benefits, policyholder account balances and other policy-related balances	99,404	89,422
Latin America
Insurance Liabilities [Line Items]
Insurance liabilities comprised of future policy benefits, policyholder account balances and other policy-related balances	16,758	14,760
EMEA
Insurance Liabilities [Line Items]
Insurance liabilities comprised of future policy benefits, policyholder account balances and other policy-related balances	19,579	18,075
MetLife Holdings
Insurance Liabilities [Line Items]
Insurance liabilities comprised of future policy benefits, policyholder account balances and other policy-related balances	103,372	104,271
Corporate & Other
Insurance Liabilities [Line Items]
Insurance liabilities comprised of future policy benefits, policyholder account balances and other policy-related balances	$ 829	$ (3,121)