Condensed Financial Information (Parent Company) (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net income (loss)	$ 2,067	$ 912	$ 891	$ 1,253	$ 2,317	$ (91)	$ 911	$ 873	$ 5,123	$ 4,010	$ 850
(Gains) losses on investments and from sales of businesses, net									298	363	(183)
Goodwill impairment									0	0	260
Other, net									(62)	184	139
Net cash provided by (used in) operating activities									11,738	12,283	14,774
Cash flows from investing activities
Sales of fixed maturity securities available-for-sale									106,677	95,945	150,658
Purchases of fixed maturity securities available-for-sale									(105,401)	(105,683)	(146,397)
Cash received in connection with freestanding derivatives									3,778	5,315	4,259
Cash paid in connection with freestanding derivatives									(4,173)	(8,696)	(6,963)
Net change in short-term investments									870	2,087	1,270
Other, net									(32)	(346)	(457)
Net cash provided by (used in) investing activities									(5,634)	(16,876)	(5,850)
Cash flows from financing activities
Net change in payables for collateral under securities loaned and other transactions									(821)	903	(3,636)
Long-term debt repaid									(1,871)	(1,073)	(1,279)
Treasury stock acquired in connection with share repurchases									(3,992)	(2,927)	(372)
Preferred stock issued, net of issuance costs									1,274	0	0
Dividends on preferred stock									(141)	(103)	(103)
Dividends on common stock									(1,678)	(1,717)	(1,736)
Other, net									(145)	118	139
Net cash provided by (used in) financing activities									(2,801)	(906)	(3,497)
Change in cash and cash equivalents									3,120	(5,176)	5,125
Cash and cash equivalents, from continuing operations, beginning of year				12,701				12,651	12,701	12,651	11,182
Cash and cash equivalents, from continuing operations, end of year	15,821				12,701				15,821	12,701	12,651
Supplemental disclosures of cash flow information:
Net cash paid (received) for Income tax									1,935	1,530	672
Non-cash transactions
Distribution of Brighthouse										(11,666)
Reduction of long-term debt									944	0	0
Reduction of fair value option securities									1,030	0	0
Parent Company
Cash flows from operating activities
Net income (loss)									5,123	4,010	850
Earnings of subsidiaries									(6,466)	(7,162)	(1,833)
Dividends from subsidiaries									7,367	6,745	4,470
(Gains) losses on investments and from sales of businesses, net									277	1,142	(86)
Goodwill impairment									0	0	147
Tax separation agreement charge									0	1,093	0
Other, net									(807)	634	199
Net cash provided by (used in) operating activities									5,494	6,462	3,747
Cash flows from investing activities
Sales of fixed maturity securities available-for-sale									9,635	7,217	8,603
Purchases of fixed maturity securities available-for-sale									(8,178)	(7,733)	(7,409)
Cash received in connection with freestanding derivatives									227	452	311
Cash paid in connection with freestanding derivatives									(237)	(629)	(561)
Sales of businesses									0	0	291
Expense paid on behalf of subsidiaries									(14)	(42)	(68)
Receipts on loans to subsidiaries									0	0	140
Issuances of loans to subsidiaries									0	0	(140)
Returns of capital from subsidiaries									87	610	80
Capital contributions to subsidiaries									(767)	(339)	(1,733)
Net change in short-term investments									14	118	120
Other, net									(3)	(14)	(18)
Net cash provided by (used in) investing activities									764	(360)	(384)
Cash flows from financing activities
Net change in payables for collateral under securities loaned and other transactions									(27)	(111)	(80)
Long-term debt repaid									(1,759)	(1,000)	(1,250)
Fees paid for the termination of a committed facility related to Separation									0	(244)	(2)
Treasury stock acquired in connection with share repurchases									(3,992)	(2,927)	(372)
Preferred stock issued, net of issuance costs									1,274	0	0
Dividends on preferred stock									(141)	(103)	(103)
Dividends on common stock									(1,678)	(1,717)	(1,736)
Other, net									(75)	182	93
Net cash provided by (used in) financing activities									(6,398)	(5,920)	(3,450)
Change in cash and cash equivalents									(140)	182	(87)
Cash and cash equivalents, from continuing operations, beginning of year				$ 516				$ 334	516	334	421
Cash and cash equivalents, from continuing operations, end of year	$ 376				$ 516				376	516	334
Supplemental disclosures of cash flow information:
Net cash paid for Interest									1,040	1,096	1,146
Net cash paid (received) for Income tax									877	(860)	(433)
Non-cash transactions
Dividends from subsidiary									0	0	2,652
Returns of capital from subsidiaries									3,844	17,518	372
Capital contributions to subsidiaries									3,844	15,655	157
Distribution of Brighthouse									0	10,346	0
Allocation of interest expense to subsidiary									0	15	39
Allocation of interest income to subsidiary									0	4	54
Reduction of long-term debt									944	0	0
Reduction of fair value option securities									1,030	0	0
Amounts paid to (received from) subsidiaries, net | Parent Company
Supplemental disclosures of cash flow information:
Net cash paid (received) for Income tax									(33)	(1,552)	(569)
Amounts paid to Brighthouse in accordance with the tax separation agreement
Supplemental disclosures of cash flow information:
Net cash paid (received) for Income tax									909
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									909	729	0
Income tax paid (received) by MetLife, Inc., net | Parent Company
Supplemental disclosures of cash flow information:
Net cash paid (received) for Income tax									$ 1	$ (37)	$ 136