Concentrations of Credit Risk Concentration of Credit Risk (Narrative) (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Mar. 07, 2014 PMI Mortgage Insurance Co. [Member]	Dec. 31, 2013 PMI Mortgage Insurance Co. [Member]	Jul. 01, 2014 Republic Mortgage Insurance Company and Affiliate [Member]	Jun. 30, 2014 Republic Mortgage Insurance Company and Affiliate [Member]	Jun. 30, 2014 Mortgage Sellers and Servicers [Member]	Dec. 31, 2013 Mortgage Sellers and Servicers [Member]	Jun. 30, 2014 Guaranty Book of Business [Member] Single-Family [Member] insurers servicers	Dec. 31, 2013 Guaranty Book of Business [Member] Single-Family [Member] insurers servicers	Jun. 30, 2014 Guaranty Book of Business [Member] Single-Family [Member] Unpaid Principal Balance [Member]	Dec. 31, 2013 Guaranty Book of Business [Member] Single-Family [Member] Unpaid Principal Balance [Member]	Jun. 30, 2014 Guaranty Book of Business [Member] Single-Family [Member] Unpaid Principal Balance [Member] Credit Concentration Risk [Member] Largest Mortgage Servicers, Including Their Affiliates [Member]	Dec. 31, 2013 Guaranty Book of Business [Member] Single-Family [Member] Unpaid Principal Balance [Member] Credit Concentration Risk [Member] Largest Mortgage Servicers, Including Their Affiliates [Member]	Jun. 30, 2014 Guaranty Book of Business [Member] Single-Family [Member] Unpaid Principal Balance [Member] Insurance Service Provider Concentration Risk [Member]	Jun. 30, 2014 Guaranty Book of Business [Member] Single-Family [Member] Unpaid Principal Balance [Member] Insurance Service Provider Concentration Risk [Member] Mortgage Insurance Companies [Member]	Dec. 31, 2013 Guaranty Book of Business [Member] Single-Family [Member] Unpaid Principal Balance [Member] Insurance Service Provider Concentration Risk [Member] Mortgage Insurance Companies [Member]	Jun. 30, 2014 Guaranty Book of Business [Member] Multifamily [Member] servicers	Dec. 31, 2013 Guaranty Book of Business [Member] Multifamily [Member] servicers	Jun. 30, 2014 Guaranty Book of Business [Member] Multifamily [Member] Unpaid Principal Balance [Member] Credit Concentration Risk [Member] Largest Mortgage Servicers, Including Their Affiliates [Member]	Dec. 31, 2013 Guaranty Book of Business [Member] Multifamily [Member] Unpaid Principal Balance [Member] Credit Concentration Risk [Member] Largest Mortgage Servicers, Including Their Affiliates [Member]
Concentration of Credit Risk [Line Items]
Number of mortgage servicers, including their affiliates, which serviced the majority of our guaranty book of business									5	5								10	10
Percentage of concentration risk													48.00%	49.00%	13.00%	79.00%	78.00%			66.00%	65.00%
Mortgage insurance coverage risk in force											$ 104,600,000,000	$ 102,500,000,000
Mortgage insurance coverage risk in force as percentage											4.00%	4.00%
Primary mortgage insurance coverage risk in force											103,600,000,000	101,400,000,000
Pool mortgage insurance coverage risk in force											959,000,000	1,100,000,000
Number of mortgage insurance companies provided majority of our mortgage insurance									4	4
Number of mortgage Insurers publicly disclosed credit quality deterioration									3
Mortgage insurance coverage risk in force, insurers with credit quality deterioration															13,500,000,000
Mortgage insurance coverage risk in force, Insurance claim, percentage to be paid in cash by mortgage insurer			67.00%	55.00%	100.00%	60.00%
Receivable from claims on insured, defaulted loans excluding government insured loans	2,000,000,000	2,100,000,000					328,000,000	402,000,000
Allowance for mortgage insurance receivable	$ 611,000,000	$ 655,000,000