Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Investments:
Amortized cost of fixed maturity securities available-for-sale	$ 342,533	$ 340,870
Fixed maturity securities relating to variable interest entities	374,294	374,266
Cost of equity securities available-for-sale	2,898	2,838
Actively traded securities	792	659
Fair value option and trading securities relating to variable interest entities	16,588	16,348
Mortgage loans:
Valuation allowances for held-for-investment	332	347
Mortgage loans, at estimated fair value, relating to variable interest entities	55,343	56,592
Mortgage loans held-for-sale under fair value option	2	49
Policy loans	11,781	11,884
Real estate and real estate joint ventures relating to variable interest entities	9,998	9,918
Other limited partnership interests relating to variable interest entities	7,087	6,688
Short-term investments	13,653	16,906
Other invested assets relating to variable interest entities	20,269	21,145
Cash and cash equivalents relating to variable interest entities	9,983	15,738
Accrued investment income relating to variable interest entities	4,555	4,374
Premiums, reinsurance and other receivables relating to variable interest entities	23,052	21,634
Deferred policy acquisition costs and value of business acquired relating to variable interest entities	24,645	24,761
Other assets relating to variable interest entities	8,062	7,876
Separate account assets	249,220	235,393
Liabilities
Future policy benefits relating to variable interest entities	190,054	192,351
Policyholder account balances	224,044	225,821
Other policy-related balances relating to variable interest entities	15,472	15,463
Long-term debt, at estimated fair value, relating to variable interest entities	18,721	19,062
Other liabilities relating to variable interest entities	24,260	22,492
Separate account liabilities	249,220	235,393
MetLife, Inc.'s stockholders' equity:
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	200,000,000	200,000,000
Preferred stock, shares issued	84,000,000	84,000,000
Preferred stock, shares outstanding	84,000,000	84,000,000
Preferred stock, aggregate liquidation preference	$ 2,100	$ 2,100
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	3,000,000,000	3,000,000,000
Common stock, shares issued	1,097,412,771	1,094,880,623
Common stock, shares outstanding	1,094,218,884	1,091,686,736
Treasury stock, shares	3,193,887	3,193,887
Variable interest entities [Member]
Investments:
Fixed maturity securities relating to variable interest entities	3,873	3,378
Fair value option and trading securities relating to variable interest entities	101	112
Mortgage loans:
Mortgage loans, at estimated fair value, relating to variable interest entities	2,454	2,715
Policy loans	3	0
Real estate and real estate joint ventures relating to variable interest entities	10	10
Other limited partnership interests relating to variable interest entities	156	274
Short-term investments	14	0
Other invested assets relating to variable interest entities	81	81
Cash and cash equivalents relating to variable interest entities	208	99
Accrued investment income relating to variable interest entities	30	13
Premiums, reinsurance and other receivables relating to variable interest entities	20	5
Deferred policy acquisition costs and value of business acquired relating to variable interest entities	299	0
Other assets relating to variable interest entities	149	5
Separate account assets	1,218	0
Liabilities
Future policy benefits relating to variable interest entities	475	0
Policyholder account balances	71	0
Other policy-related balances relating to variable interest entities	145	0
Long-term debt, at estimated fair value, relating to variable interest entities	2,268	2,527
Other liabilities relating to variable interest entities	109	40
Separate account liabilities	$ 1,218	$ 0