Condensed Financial Information (Parent Company) (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net income (loss)	$ 2,317	$ (91)	$ 911	$ 873	$ (2,343)	$ 542	$ 321	$ 2,330	$ 4,010	$ 850	$ 5,373
(Gains) losses on investments and from sales of businesses, net									363	(183)	(560)
Goodwill impairment									0	260	0
Other, net									184	139	94
Net cash provided by (used in) operating activities									12,283	14,774	14,052
Cash flows from investing activities
Sales of fixed maturity securities									95,945	150,658	146,732
Purchases of fixed maturity securities									(105,683)	(146,397)	(148,799)
Cash received in connection with freestanding derivatives									5,315	4,259	2,690
Cash paid in connection with freestanding derivatives									(8,696)	(6,963)	(4,211)
Net change in short-term investments									2,087	1,270	(777)
Other, net									(346)	(457)	(59)
Net cash provided by (used in) investing activities									(16,876)	(5,850)	(10,398)
Cash flows from financing activities
Net change in payables for collateral under securities loaned and other transactions									903	(3,636)	1,544
Long-term debt issued									3,657	0	3,893
Long-term debt repaid									(1,073)	(1,279)	(1,438)
Treasury stock acquired in connection with share repurchases									(2,927)	(372)	(1,930)
Preferred stock issued, net of issuance costs									0	0	1,483
Repurchase of preferred stock									0	0	(1,460)
Preferred stock repurchase premium									0	0	(42)
Dividends on preferred stock									(103)	(103)	(116)
Dividends on common stock									(1,717)	(1,736)	(1,653)
Other, net									118	139	94
Net cash provided by (used in) financing activities									(906)	(3,497)	(1,218)
Change in cash and cash equivalents									(5,176)	5,125	1,944
Cash and cash equivalents, from continuing operations, beginning of year				12,651				11,182	12,651	11,182	9,205
Cash and cash equivalents, from continuing operations, end of year	12,701				12,651				12,701	12,651	11,182
Supplemental disclosures of cash flow information:
Net cash paid for Interest									1,118	1,202	1,178
Net cash paid (received) for Income tax									1,530	672	1,127
Non-cash transactions
Distribution of Brighthouse									(11,666)
Parent Company
Cash flows from operating activities
Net income (loss)									4,010	850	5,373
Earnings of subsidiaries									(7,162)	(1,833)	(6,048)
Dividends from subsidiaries									6,745	4,470	2,335
(Gains) losses on investments and from sales of businesses, net									1,142	(86)	(12)
Goodwill impairment									0	147	0
Tax separation agreement charge									1,093	0	0
Other, net									634	199	(42)
Net cash provided by (used in) operating activities									6,462	3,747	1,606
Cash flows from investing activities
Sales of fixed maturity securities									7,217	8,603	7,952
Purchases of fixed maturity securities									(7,733)	(7,409)	(7,957)
Cash received in connection with freestanding derivatives									452	311	930
Cash paid in connection with freestanding derivatives									(629)	(561)	(510)
Sales of businesses									0	291	0
Expense paid on behalf of subsidiaries									(42)	(68)	(40)
Receipts on loans to subsidiaries									0	140	761
Issuances of loans to subsidiaries									0	(140)	(300)
Returns of capital from subsidiaries									610	80	5
Capital contributions to subsidiaries									(339)	(1,733)	(667)
Net change in short-term investments									118	120	110
Other, net									(14)	(18)	2
Net cash provided by (used in) investing activities									(360)	(384)	286
Cash flows from financing activities
Net change in payables for collateral under securities loaned and other transactions									(111)	(80)	(122)
Long-term debt issued									0	0	2,739
Long-term debt repaid									(1,000)	(1,250)	(1,000)
Fees paid for the termination of a committed facility related to Separation									(244)	(2)	0
Treasury stock acquired in connection with share repurchases									(2,927)	(372)	(1,930)
Preferred stock issued, net of issuance costs									0	0	1,483
Repurchase of preferred stock									0	0	(1,460)
Preferred stock repurchase premium									0	0	(42)
Dividends on preferred stock									(103)	(103)	(116)
Dividends on common stock									(1,717)	(1,736)	(1,653)
Other, net									182	93	187
Net cash provided by (used in) financing activities									(5,920)	(3,450)	(1,914)
Change in cash and cash equivalents									182	(87)	(22)
Cash and cash equivalents, from continuing operations, beginning of year				$ 334				$ 421	334	421	443
Cash and cash equivalents, from continuing operations, end of year	$ 516				$ 334				516	334	421
Supplemental disclosures of cash flow information:
Net cash paid for Interest									1,096	1,146	1,133
Net cash paid (received) for Income tax									(860)	(433)	(171)
Non-cash transactions
Dividends from subsidiary									0	2,652	0
Returns of capital from subsidiaries									17,518	372	4,284
Capital contributions to subsidiaries									15,655	157	4,120
Distribution of Brighthouse									10,346	0	0
Payables to subsidiaries for future capital contributions									0	0	120
Allocation of interest expense to subsidiary									15	39	28
Allocation of interest income to subsidiary									4	54	57
Amounts paid to (received from) subsidiaries, net | Parent Company
Supplemental disclosures of cash flow information:
Net cash paid (received) for Income tax									(1,552)	(569)	(226)
Amounts paid to Brighthouse in accordance with the tax separation agreements | Parent Company
Supplemental disclosures of cash flow information:
Net cash paid (received) for Income tax									729	0	0
Income tax paid (received) by MetLife, Inc., net | Parent Company
Supplemental disclosures of cash flow information:
Net cash paid (received) for Income tax									$ (37)	$ 136	$ 55