Litigation and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Countrywide dispute [Abstract]
Number of rescindable loans affected by Company's decision to suspend rescissions for Countrywide	2,150
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions for Countrywide	$ 160,000,000
Number of rescindable loans affected by Company's decision to suspend rescissions for a specific customer	250
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions for a specific customer	17,000,000
Increase in loss reserves for the probable settlement agreements	100,000,000
Freddie Mac dispute [Abstract]
Obligations under the Disputed Policies	267,500,000
Other Legal Proceedings [Abstract]
Underwriting remedy expense	27,000,000	23,000,000	19,000,000
Class Action Complaint Under RESPA [Member] | Pending Litigation [Member]
Class action complaint under RESPA [Abstract]
Number of lawsuits	12
Number of cases dismissed	3
Number of similar cases filed naming various mortgage lenders and mortgage insurers as defendants	9
Class action lawsuit alleging discrimination [Member] | U.S. District Court for the Western District of Pennsylvania [Member] | Pending Litigation [Member]
Housing discrimination complaint [Abstract]
Settlement agreement date	2012-11-29
Number of borrowers under settlement class	265
Escrow deposit	500,000
Incentive fee	7,500
Counsels fees paid	337,500
Countrywide Dispute [Member]
Countrywide dispute [Abstract]
Average paid claim reduction due to curtailments (in hundredths)	4.00%
Number of days after claim paid within which objection must be received for review	90 days
Curtailment and other adjustments objected	40,000,000
Countrywide Dispute [Member] | Pending Litigation [Member]
Countrywide dispute [Abstract]
Amount of damages sought	700,000,000
Mitigation of paid losses	445,000,000
Number of rescindable loans affected by Company's decision to suspend rescissions for Countrywide	2,150
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions for Countrywide	160,000,000
Number of rescindable loans affected by Company's decision to suspend rescissions for a specific customer	250
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions for a specific customer	17,000,000
Increase in loss reserves for the probable settlement agreements	100,000,000
Mitigation of incurred losses since January 2008	2,900,000,000
Mitigation on paid losses, excluding deductible amounts	2,900,000,000
Amount excluded from mitigation losses that would have been applied to a deductible	600,000,000
Total loss reserves, estimated benefit from rescissions	200,000,000
Freddie Mac's disagreement on aggregate loss limit [Member]
Freddie Mac dispute [Abstract]
Obligations under the Disputed Policies	267,500,000
Amount paid as per settlement agreement	100,000,000
Remaining amount of unpaid settlement agreement	167,500,000
Number of installments to pay settlement agreement amount	48
Additional settlement payment for default on or after December 1, 2015	57,500,000
Additional settlement payment for default Default occurring on or after December 1, 2014, but before December 1, 2015	82,500,000
Additional settlement payment for default before December 1, 2014	132,500,000
Maximum amount of damages sought in case of default	$ 540,000,000
Lawsuits alleging improper recording and foreclosure activities by MERS [Member] | Pending Litigation [Member]
Lawsuits alleging improper recording and foreclosure activities by MERS [Abstract]
Number of lawsuits naming non-insurance subsidiary as defendant	9
Number of cases pending	3
Number of other lawsuits naming subsidiary as defendant that were dismissed	6