Liability for Policy and Contract Claims (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	$ 8,043	$ 7,204
Long-term Care Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	6,216	4,999	4,655	4,130
U.S. Mortgage Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	1,180	1,482	2,009	2,488
International Mortgage Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	308	378
Life Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	197	188
Lifestyle Protection Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	106	108
Fixed Annuities
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	21	29
Runoff
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	$ 15	$ 20