Summary of Total Assets for Segments and Corporate and Other Activities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total assets	$ 107,576	$ 113,312
Segment, Continuing Operations
Segment Reporting Information [Line Items]
Total assets	107,133	112,873
Segment, Continuing Operations | U.S. Life Insurance
Segment Reporting Information [Line Items]
Total assets	76,666	79,214
Segment, Continuing Operations | International Mortgage Insurance
Segment Reporting Information [Line Items]
Total assets	9,162	10,063
Segment, Continuing Operations | U.S. Mortgage Insurance
Segment Reporting Information [Line Items]
Total assets	2,158	2,357
Segment, Continuing Operations | International Protection
Segment Reporting Information [Line Items]
Total assets	2,017	2,145
Segment, Continuing Operations | Runoff
Segment Reporting Information [Line Items]
Total assets	14,065	15,308
Segment, Continuing Operations | Corporate and Other
Segment Reporting Information [Line Items]
Total assets	3,065	3,786
Segment, Discontinued Operations
Segment Reporting Information [Line Items]
Total assets	$ 443	$ 439