Previously Securitized Loans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012 item	Dec. 31, 2011	Dec. 31, 2010
Previously Securitized Loans [Abstract]
Number of securitization transactions	6
Proceeds from securitization transactions	$ 760
Fixed rate of junior-lien underlying mortgages	125.00%
Outstanding balance of securitized loans	7.8
Recognized interest income from previously securitized loans	$ 3.3	$ 3.1	$ 4.0

This is the principal amount outstanding for securitized loans only (across all types of loans).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 140

-Paragraph 17

-Subparagraph i

-Subclause a

-Clause 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS140-4/FIN46(R)-8

-Paragraph B11

-Subparagraph b

-Clause 6

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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