Fair Value - Significant Unobservable Inputs Used for Assets Measured at Fair Value on Non-Recurring Basis (Detail) (Fair value, non-recurring basis [Member], Real estate owned, net [Member])	9 Months Ended
Sep. 30, 2013
Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	0.00%
Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	74.20%
Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	10.17%

Loss, including interest and principal, incurred on a defaulted security, expressed as a percentage of the original principal balance, used as an input to measure fair value.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

Name:	us-gaap_FairValueInputsLossSeverity
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration