Investments (Credit Quality of Mortgage Loans by Portfolio Segment) (Details) - Mortgage Loans - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current FY	$ 36	$ 78
Financing receivable, originated in FY before latest FY	76	198
Financing receivable, originated two years before latest FY	195	56
Financing receivable, originated three years before latest FY	56	26
Financing receivable, originated four years before latest FY	26	32
Financing receivable, originated five or more years before latest FY	244	255
Financing receivable, before allowance for credit losses	633	645
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current FY	17	32
Financing receivable, originated in FY before latest FY	31	152
Financing receivable, originated two years before latest FY	152	34
Financing receivable, originated three years before latest FY	35	20
Financing receivable, originated four years before latest FY	20	17
Financing receivable, originated five or more years before latest FY	195	203
Financing receivable, before allowance for credit losses	$ 450	$ 458
Financing receivable, before allowance for credit losses by debt service coverage ratio as a percentage of financing receivable, before allowance for credit losses	100.00%	100.00%
Commercial \| Debt Service Coverage Ratio, Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, before allowance for credit losses	$ 434	$ 450
Financing receivable, before allowance for credit losses by debt service coverage ratio as a percentage of financing receivable, before allowance for credit losses	96.40%	98.30%
Commercial \| Debt Service Coverage Ratio, 1.00x to 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, before allowance for credit losses	$ 9	$ 8
Financing receivable, before allowance for credit losses by debt service coverage ratio as a percentage of financing receivable, before allowance for credit losses	2.00%	1.70%
Commercial \| Debt Service Coverage Ratio, Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, before allowance for credit losses	$ 7	$ 0
Financing receivable, before allowance for credit losses by debt service coverage ratio as a percentage of financing receivable, before allowance for credit losses	1.60%	0.00%
Commercial \| Loan-to-Value Ratio, Less than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current FY	$ 17	$ 32
Financing receivable, originated in FY before latest FY	31	102
Financing receivable, originated two years before latest FY	87	23
Financing receivable, originated three years before latest FY	24	13
Financing receivable, originated four years before latest FY	13	16
Financing receivable, originated five or more years before latest FY	179	187
Financing receivable, before allowance for credit losses	351	373
Commercial \| Loan-to-Value Ratio, 65% to 75%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current FY	0	0
Financing receivable, originated in FY before latest FY	0	50
Financing receivable, originated two years before latest FY	65	6
Financing receivable, originated three years before latest FY	6	7
Financing receivable, originated four years before latest FY	7	0
Financing receivable, originated five or more years before latest FY	2	3
Financing receivable, before allowance for credit losses	80	66
Commercial \| Loan-to-Value Ratio, 76% to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current FY	0	0
Financing receivable, originated in FY before latest FY	0	0
Financing receivable, originated two years before latest FY	0	0
Financing receivable, originated three years before latest FY	0	0
Financing receivable, originated four years before latest FY	0	1
Financing receivable, originated five or more years before latest FY	4	3
Financing receivable, before allowance for credit losses	4	4
Commercial \| Loan-to-Value Ratio, Greater than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current FY	0	0
Financing receivable, originated in FY before latest FY	0	0
Financing receivable, originated two years before latest FY	0	5
Financing receivable, originated three years before latest FY	5	0
Financing receivable, originated four years before latest FY	0	0
Financing receivable, originated five or more years before latest FY	10	10
Financing receivable, before allowance for credit losses	15	15
Agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current FY	19	46
Financing receivable, originated in FY before latest FY	45	46
Financing receivable, originated two years before latest FY	43	22
Financing receivable, originated three years before latest FY	21	6
Financing receivable, originated four years before latest FY	6	15
Financing receivable, originated five or more years before latest FY	49	52
Financing receivable, before allowance for credit losses	183	187
Agricultural \| Loan-to-Value Ratio, Less than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current FY	19	46
Financing receivable, originated in FY before latest FY	45	43
Financing receivable, originated two years before latest FY	41	21
Financing receivable, originated three years before latest FY	20	6
Financing receivable, originated four years before latest FY	6	15
Financing receivable, originated five or more years before latest FY	49	52
Financing receivable, before allowance for credit losses	180	183
Agricultural \| Loan-to-Value Ratio, 65% to 75%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current FY	0	0
Financing receivable, originated in FY before latest FY	0	3
Financing receivable, originated two years before latest FY	2	1
Financing receivable, originated three years before latest FY	1	0
Financing receivable, originated four years before latest FY	0	0
Financing receivable, originated five or more years before latest FY	0	0
Financing receivable, before allowance for credit losses	$ 3	$ 4

BRIGHTHOUSE LIFE INSURANCE Co OF NY 10-Q