Condensed Financial Information (Parent Company) (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income (loss)	$ 593	$ 2,184	$ 1,741	$ 1,381	$ 2,067	$ 912	$ 891	$ 1,253	$ 5,899	$ 5,123	$ 4,010
(Gains) losses on investments and from sales of businesses, net									(444)	298	363
Other, net									285	(62)	184
Net cash provided by (used in) operating activities									13,786	11,738	12,283
Cash flows from investing activities
Sales of fixed maturity securities available-for-sale									77,820	106,677	95,945
Purchases of fixed maturity securities available-for-sale									(87,455)	(105,401)	(105,683)
Cash received in connection with freestanding derivatives									2,914	3,778	5,315
Cash paid in connection with freestanding derivatives									(3,749)	(4,173)	(8,696)
Net change in short-term investments									152	870	2,087
Other, net									(131)	(32)	(346)
Net cash provided by (used in) investing activities									(17,586)	(5,634)	(16,876)
Cash flows from financing activities
Net change in payables for collateral under securities loaned and other transactions									2,019	(821)	903
Long-term debt issued									1,382	24	3,657
Long-term debt repaid									(906)	(1,871)	(1,073)
Treasury stock acquired in connection with share repurchases									(2,285)	(3,992)	(2,927)
Preferred stock issued, net of issuance costs									0	1,274	0
Dividends on preferred stock									(178)	(141)	(103)
Dividends on common stock									(1,643)	(1,678)	(1,717)
Other, net									(77)	(145)	118
Net cash provided by (used in) financing activities									4,568	(2,801)	(906)
Cash and cash equivalents, from continuing operations, beginning of year				15,821					15,821
Cash and cash equivalents, from continuing operations, end of year	16,598				15,821				16,598	15,821
Supplemental disclosures of cash flow information
Net cash paid (received) for Income tax									1,099	1,935	1,530
Non-cash transactions
Distribution of Brighthouse											(11,666)
Reduction of long-term debt									0	944	0
Reduction of fair value option securities									0	1,030	0
Parent Company
Cash flows from operating activities
Net income (loss)									5,899	5,123	4,010
Earnings of subsidiaries									(6,301)	(6,466)	(7,162)
Dividends from subsidiaries									4,790	7,367	6,745
(Gains) losses on investments and from sales of businesses, net									40	277	1,142
Tax separation agreement charge									0	0	1,093
Other, net									(251)	(807)	634
Net cash provided by (used in) operating activities									4,177	5,494	6,462
Cash flows from investing activities
Sales of fixed maturity securities available-for-sale									3,153	9,635	7,217
Purchases of fixed maturity securities available-for-sale									(3,380)	(8,178)	(7,733)
Cash received in connection with freestanding derivatives									101	227	452
Cash paid in connection with freestanding derivatives									(392)	(237)	(629)
Expense paid on behalf of subsidiaries									(13)	(14)	(42)
Returns of capital from subsidiaries									10	87	610
Capital contributions to subsidiaries									(75)	(767)	(339)
Net change in short-term investments									14	14	118
Other, net									28	(3)	(14)
Net cash provided by (used in) investing activities									(554)	764	(360)
Cash flows from financing activities
Net change in payables for collateral under securities loaned and other transactions									7	(27)	(111)
Long-term debt issued									1,382	0	0
Long-term debt repaid									(877)	(1,759)	(1,000)
Fees paid for the termination of a committed facility related to Separation									0	0	(244)
Treasury stock acquired in connection with share repurchases									(2,285)	(3,992)	(2,927)
Preferred stock issued, net of issuance costs									0	1,274	0
Dividends on preferred stock									(178)	(141)	(103)
Dividends on common stock									(1,643)	(1,678)	(1,717)
Other, net									(28)	(75)	182
Net cash provided by (used in) financing activities									(3,622)	(6,398)	(5,920)
Change in cash and cash equivalents									1	(140)	182
Cash and cash equivalents, from continuing operations, beginning of year				$ 376				$ 516	376	516	334
Cash and cash equivalents, from continuing operations, end of year	$ 377				$ 376				377	376	516
Supplemental disclosures of cash flow information
Net cash paid for Interest									864	1,040	1,096
Net cash paid (received) for Income tax									(155)	877	(860)
Non-cash transactions
Returns of capital from subsidiaries									29	3,844	17,518
Capital contributions to subsidiaries									30	3,844	15,655
Distribution of Brighthouse									0	0	10,346
Allocation of interest expense to subsidiary									0	0	15
Allocation of interest income to subsidiary									0	0	4
Reduction of long-term debt									0	944	0
Reduction of fair value option securities									0	1,030	0
Amounts paid to (received from) subsidiaries, net | Parent Company
Supplemental disclosures of cash flow information
Net cash paid (received) for Income tax									(152)	(33)	(1,552)
Amounts paid to Brighthouse in accordance with the tax separation agreement | Parent Company
Supplemental disclosures of cash flow information
Net cash paid (received) for Income tax									0	909	729
Income tax paid (received) by MetLife, Inc., net | Parent Company
Supplemental disclosures of cash flow information
Net cash paid (received) for Income tax									$ (3)	$ 1	$ (37)