Distribution Across Property Type and Geographic Region for Commercial Mortgage Loans (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	$ 6,013	$ 5,932
Allowance for losses	(27)	(33)
% of total	100.00%	100.00%
Total	5,986	5,899
Commercial Mortgage Loan
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	6,013	5,932
Allowance for losses	(27)	(33)
% of total	100.00%	100.00%
Total	5,986	5,899
Pacific | Commercial Mortgage Loan
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	1,607	1,590
% of total	27.00%	27.00%
South Atlantic | Commercial Mortgage Loan
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	1,565	1,535
% of total	26.00%	26.00%
Middle Atlantic | Commercial Mortgage Loan
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	812	828
% of total	13.00%	14.00%
Mountain | Commercial Mortgage Loan
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	514	478
% of total	9.00%	8.00%
East North Central | Commercial Mortgage Loan
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	409	404
% of total	7.00%	7.00%
West North Central | Commercial Mortgage Loan
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	366	377
% of total	6.00%	6.00%
New England | Commercial Mortgage Loan
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	350	337
% of total	6.00%	6.00%
West South Central | Commercial Mortgage Loan
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	254	241
% of total	4.00%	4.00%
East South Central | Commercial Mortgage Loan
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	136	142
% of total	2.00%	2.00%
Retail
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	2,162	2,073
% of total	36.00%	35.00%
Industrial
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	1,585	1,581
% of total	26.00%	27.00%
Office
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	1,533	1,558
% of total	26.00%	26.00%
Apartments
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	480	491
% of total	8.00%	8.00%
Mixed use/other
Distribution of Commercial Mortgage Loans [Line Items]
Commercial mortgage loans, recorded investment	$ 253	$ 229
% of total	4.00%	4.00%