Capital Requirements (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016 USD ($) jurisdiction	Dec. 31, 2015 USD ($)
Statutory capital requirements [Abstract]
Number of jurisdictions with risk-to-capital requirements | jurisdiction	16
Maximum permitted risk-to-capital ratio commonly applied	25 to 1
Risk to capital ratio of combined insurance operations, including reinsurance affiliates, at end of period	13.8 to 1
Risk-to-capital ratio for combined insurance operations	13.8
Percentage of statutory policyholders surplus used to determine maximum allowable dividends	10.00%
Maximum
Statutory capital requirements [Abstract]
Risk-to-capital ratio	25
Mortgage Guaranty Insurance Corporation
Statutory capital requirements [Abstract]
Risk to capital ratio at end of period	12.3 to 1
Risk-to-capital ratio	12.3
Amount of policyholders position above or below required MPP	$ 1,100
Amount of required MPP	1,100
Dividends paid to the parent company	$ 16
Adjusted statutory net income measurement period	3 years
Adjusted statutory net income dividend payment measurement period	2 years
Reduction in statutory net income due to increase in contingency reserve		$ 444