Loan-to-Value of Restricted Commercial Mortgage Loans by Property Type (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	$ 5,868		$ 5,912
% of total	100.00%		100.00%
Weighted-average debt service coverage ratio	1.84		1.95
Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	2,000		1,895
% of total	34.00%		32.00%
Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	1,565		1,603
% of total	27.00%		27.00%
Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	1,585		1,580
% of total	27.00%		27.00%
Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	490		552
% of total	8.00%		9.00%
Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	228		282
% of total	4.00%		5.00%
Restricted commercial mortgage loans related to securitization entities
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	310		342
% of total	100.00%		100.00%
Weighted-average debt service coverage ratio	1.69		1.68
Restricted commercial mortgage loans related to securitization entities | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	125		140
Restricted commercial mortgage loans related to securitization entities | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	72		81
Restricted commercial mortgage loans related to securitization entities | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	59		63
Restricted commercial mortgage loans related to securitization entities | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	51		53
Restricted commercial mortgage loans related to securitization entities | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	3		5
0% - 50%
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	1,668		1,568
% of total	29.00%		27.00%
Weighted-average debt service coverage ratio	2.38		2.13
0% - 50% | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	565		548
0% - 50% | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	451		462
0% - 50% | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	374		323
0% - 50% | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	199		167
0% - 50% | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	79		68
0% - 50% | Restricted commercial mortgage loans related to securitization entities
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	263		290
% of total	84.00%		85.00%
Weighted-average debt service coverage ratio	1.76		1.78
0% - 50% | Restricted commercial mortgage loans related to securitization entities | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	112		126
0% - 50% | Restricted commercial mortgage loans related to securitization entities | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	68		77
0% - 50% | Restricted commercial mortgage loans related to securitization entities | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	52		54
0% - 50% | Restricted commercial mortgage loans related to securitization entities | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	28		28
0% - 50% | Restricted commercial mortgage loans related to securitization entities | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	3		5
51% - 60%
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	935		923
% of total	16.00%		16.00%
Weighted-average debt service coverage ratio	1.75		1.73
51% - 60% | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	361		280
51% - 60% | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	215		242
51% - 60% | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	217		237
51% - 60% | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	93		140
51% - 60% | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	49		24
51% - 60% | Restricted commercial mortgage loans related to securitization entities
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	8		11
% of total	3.00%		3.00%
Weighted-average debt service coverage ratio	1.38		1.38
51% - 60% | Restricted commercial mortgage loans related to securitization entities | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	4		4
51% - 60% | Restricted commercial mortgage loans related to securitization entities | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		0
51% - 60% | Restricted commercial mortgage loans related to securitization entities | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	1		3
51% - 60% | Restricted commercial mortgage loans related to securitization entities | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	3		4
51% - 60% | Restricted commercial mortgage loans related to securitization entities | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		0
61% - 75%
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	2,651		2,537
% of total	45.00%		42.00%
Weighted-average debt service coverage ratio	1.72		2.09
61% - 75% | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	938		874
61% - 75% | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	723		671
61% - 75% | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	733		688
61% - 75% | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	169		201
61% - 75% | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	88		103
61% - 75% | Restricted commercial mortgage loans related to securitization entities
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	34		31
% of total	11.00%		9.00%
Weighted-average debt service coverage ratio	1.42		1.14
61% - 75% | Restricted commercial mortgage loans related to securitization entities | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	6		7
61% - 75% | Restricted commercial mortgage loans related to securitization entities | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	4		3
61% - 75% | Restricted commercial mortgage loans related to securitization entities | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	4		0
61% - 75% | Restricted commercial mortgage loans related to securitization entities | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	20		21
61% - 75% | Restricted commercial mortgage loans related to securitization entities | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		0
76% - 100%
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	489		748
% of total	8.00%		13.00%
Weighted-average debt service coverage ratio	1.11		1.18
76% - 100% | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	110		162
76% - 100% | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	154		188
76% - 100% | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	197		288
76% - 100% | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	28		29
76% - 100% | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		81
76% - 100% | Restricted commercial mortgage loans related to securitization entities
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	2		7
% of total	1.00%		2.00%
Weighted-average debt service coverage ratio	0.41		0.86
76% - 100% | Restricted commercial mortgage loans related to securitization entities | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		0
76% - 100% | Restricted commercial mortgage loans related to securitization entities | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		1
76% - 100% | Restricted commercial mortgage loans related to securitization entities | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	2		6
76% - 100% | Restricted commercial mortgage loans related to securitization entities | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		0
76% - 100% | Restricted commercial mortgage loans related to securitization entities | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		0
Greater than 100%
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	125	[1]	136	[2]
% of total	2.00%	[1]	2.00%	[2]
Weighted-average debt service coverage ratio	0.63	[1]	2.48	[2]
Greater than 100% | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	26	[1]	31	[2]
Greater than 100% | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	22	[1]	40	[2]
Greater than 100% | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	64	[1]	44	[2]
Greater than 100% | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	1	[1]	15	[2]
Greater than 100% | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	12	[1]	6	[2]
Greater than 100% | Restricted commercial mortgage loans related to securitization entities
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	3		3
% of total	1.00%		1.00%
Weighted-average debt service coverage ratio	0.44		0.54
Greater than 100% | Restricted commercial mortgage loans related to securitization entities | Retail
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	3		3
Greater than 100% | Restricted commercial mortgage loans related to securitization entities | Industrial
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		0
Greater than 100% | Restricted commercial mortgage loans related to securitization entities | Office
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		0
Greater than 100% | Restricted commercial mortgage loans related to securitization entities | Apartments
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	0		0
Greater than 100% | Restricted commercial mortgage loans related to securitization entities | Mixed use/other
Commercial Mortgage Loans by Credit Quality Indicator [Line Items]
Commercial mortgage loans, recorded investment	$ 0		$ 0

[1] Included $1 million of impaired loans, $11 million of loans past due and not individually impaired and $113 million of loans in good standing where borrowers continued to make timely payments, with a total weighted-average loan-to-value of 117%.

[2] Included $136 million of loans in good standing where borrowers continued to make timely payments, with a total weighted-average loan-to-value of 144%.