Investments - Other-than-Temporary Impairments (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Document Period End Date	Dec. 31, 2013
Change-of-intent, and non-credit losses in other comprehensive income		$ 1.5

The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD.

No definition available.

Name:	dei_DocumentPeriodEndDate
Namespace Prefix:	dei_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration