Condensed Financial Information (Parent Company) (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net income (loss)	$ 158	$ 706	$ 145	$ 4,398	$ 593	$ 2,184	$ 1,741	$ 1,381	$ 5,407	$ 5,899	$ 5,123
(Gains) losses on investments and from sales of businesses, net									110	(444)	298
Other, net									351	285	(62)
Net cash provided by (used in) operating activities									11,639	13,786	11,738
Cash flows from investing activities
Sales and maturities of fixed maturity securities available-for-sale									77,979	77,820	106,677
Purchases of fixed maturity securities available-for-sale									(89,633)	(87,455)	(105,401)
Cash received in connection with freestanding derivatives									4,847	2,914	3,778
Cash paid in connection with freestanding derivatives									(4,247)	(3,749)	(4,173)
Purchases of businesses									(1,875)	0	0
Net change in short-term investments									(341)	152	870
Other, net									139	(131)	(32)
Net cash provided by (used in) investing activities									(18,569)	(17,586)	(5,634)
Cash flows from financing activities
Net change in payables for collateral under securities loaned and other transactions									3,538	2,019	(821)
Long-term debt issued									1,124	1,382	24
Long-term debt repaid									(99)	(906)	(1,871)
Treasury stock acquired in connection with share repurchases									(1,151)	(2,285)	(3,992)
Preferred stock issued, net of issuance costs									1,961	0	1,274
Redemption of preferred stock									(989)	0	0
Preferred stock redemption premium									(14)	0	0
Dividends on preferred stock									(202)	(178)	(141)
Dividends on common stock									(1,657)	(1,643)	(1,678)
Other, net									191	(77)	(145)
Net cash provided by (used in) financing activities									10,729	4,568	(2,801)
Cash and cash equivalents, from continuing operations, beginning of year				16,598					16,598
Cash and cash equivalents, from continuing operations, end of year	19,795				16,598				19,795	16,598
Supplemental disclosures of cash flow information
Net cash paid (received) for Income tax									787	1,099	1,935
Non-cash transactions:
Reduction of long-term debt									0	0	944
Reduction of fair value option securities									0	0	1,030
Parent Company
Cash flows from operating activities
Net income (loss)									5,407	5,899	5,123
Earnings of subsidiaries									(6,263)	(6,301)	(6,466)
Dividends from subsidiaries									3,970	4,790	7,367
(Gains) losses on investments and from sales of businesses, net									154	40	277
Other, net									211	(251)	(807)
Net cash provided by (used in) operating activities									3,479	4,177	5,494
Cash flows from investing activities
Sales and maturities of fixed maturity securities available-for-sale									3,693	3,153	9,635
Purchases of fixed maturity securities available-for-sale									(3,858)	(3,380)	(8,178)
Cash received in connection with freestanding derivatives									71	101	227
Cash paid in connection with freestanding derivatives									(100)	(392)	(237)
Purchases of businesses									(1,875)	0	0
Expense paid on behalf of subsidiaries									(15)	(13)	(14)
Proceeds from Collection of Long-term Loans to Related Parties									100	0	0
Returns of capital from subsidiaries									16	10	87
Capital contributions to subsidiaries									(422)	(75)	(767)
Net change in short-term investments									4	14	14
Other, net									(2)	28	(3)
Net cash provided by (used in) investing activities									(2,388)	(554)	764
Cash flows from financing activities
Net change in payables for collateral under securities loaned and other transactions									49	7	(27)
Long-term debt issued									1,246	1,382	0
Long-term debt repaid									(251)	(877)	(1,759)
Treasury stock acquired in connection with share repurchases									(1,151)	(2,285)	(3,992)
Preferred stock issued, net of issuance costs									1,961	0	1,274
Redemption of preferred stock									(989)	0	0
Preferred stock redemption premium									(14)	0	0
Dividends on preferred stock									(202)	(178)	(141)
Dividends on common stock									(1,657)	(1,643)	(1,678)
Other, net									(19)	(28)	(75)
Net cash provided by (used in) financing activities									(1,027)	(3,622)	(6,398)
Change in cash and cash equivalents									64	1	(140)
Cash and cash equivalents, from continuing operations, beginning of year				$ 377				$ 376	377	376	516
Cash and cash equivalents, from continuing operations, end of year	$ 441				$ 377				441	377	376
Supplemental disclosures of cash flow information
Net cash paid for Interest									815	864	1,040
Net cash paid (received) for Income tax									(296)	(155)	877
Non-cash transactions:
Dividends from subsidiary									341	0	0
Returns of capital from subsidiaries									13	29	3,844
Capital contributions to subsidiaries									1	30	3,844
Reduction of long-term debt									0	0	944
Reduction of fair value option securities									0	0	1,030
Amounts paid to (received from) subsidiaries, net | Parent Company
Supplemental disclosures of cash flow information
Net cash paid (received) for Income tax									(392)	(152)	(33)
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	0	909
Income tax paid (received) by MetLife, Inc., net | Parent Company
Supplemental disclosures of cash flow information
Net cash paid (received) for Income tax									$ 96	$ (3)	$ 1