Investments Mortgage Loan Restructuring (Detail) (9 months ended [Domain], Commercial Real Estate Portfolio Segment [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
9 months ended [Domain] \| Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 4.3	$ 13.1
Number of Trouble Debt Modifications Entered Into During Period	1	2

Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 34

-URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953682-111524

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant