Sale of Businesses - Additional Information (Detail) - Assets Held For Sale Related To Discontinued Operations € in Millions, $ in Millions				3 Months Ended			9 Months Ended
	Oct. 27, 2015 USD ($)	Jul. 22, 2015 USD ($)	Jul. 22, 2015 EUR (€)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Lifestyle Protection Insurance
Income Statement, Balance Sheet and Additional Disclosures by Planned Disposal Groups [Line Items]
(Loss) on Disposal of Discontinued Operation, Net of Tax				$ (12)	$ (306)	$ 0	$ (318)	$ 0
Tax Benefit from Provision for Loss on Disposal					152
Increase in estimated loss on sale of discontinued operations					(12)
Fair value less pension settlement costs and closing costs impairment					451
Pension settlement costs and closing costs					$ 124
Expected sale price		$ 490	€ 475
Expected net proceeds from sale of business, discontinued operations		$ 400
European Mortgage Insurance Business | Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Planned Disposal Groups [Line Items]
Expected net proceeds from sale of business, discontinued operations	$ 55
Loss on disposal not discontinued operations, net of tax	$ (140)