Premium Deficiency Reserve	12 Months Ended
Dec. 31, 2015
Premium Deficiency Reserve [Abstract]
Premium Deficiency Reserve	Premium Deficiency Reserve Beginning in 2007, when we stopped writing Wall Street Bulk business, we began to separately measure the performance of these transactions and establish a premium deficiency reserve related to this business. The premium deficiency reserve reflects the present value of expected future losses and expenses that exceed the present value of expected future premiums and established loss reserves. Each quarter, we re-estimate the premium deficiency reserve on the remaining Wall Street bulk insurance in force. The premium deficiency reserve primarily changes from quarter to quarter as a result of two factors. First, it changes as the actual premiums, losses and expenses that were previously estimated are recognized. Each period such items are reflected in our financial statements as earned premium, losses incurred and expenses. The difference between the amount and timing of actual earned premiums, losses incurred and expenses and our previous estimates used to establish the premium deficiency reserves has an effect (either positive or negative) on that period’s results. Second, the premium deficiency reserve changes as our assumptions relating to the present value of expected future premiums, losses and expenses on the remaining Wall Street bulk insurance in force change. Changes to these assumptions also have an effect on that period’s results. The decreases in the premium deficiency reserve for the years ended December 31, 2015, 2014 and 2013 were $24 million, $24 million, and $26 million, respectively. As of December 31, 2015, there was no premium deficiency reserve required. The decreases represent the net result of actual premiums, losses and expenses as well as a net change in assumptions for these periods. The change in assumptions for 2014 and 2013 are primarily related to higher estimated ultimate premiums resulting principally from an increase in the projected persistency rate, offset in part by higher estimated ultimate losses resulting principally from an increase in the number of projected claims that will ultimately be paid. The calculation of premium deficiency reserves requires the use of significant judgments and estimates to determine the present value of future premium and present value of expected losses and expenses on our business. The calculation of future premium depends on, among other things, assumptions about persistency and repayment patterns on underlying loans. The calculation of expected losses and expenses depends on assumptions relating to severity of claims and claim rates on current defaults, and expected defaults in future periods. These assumptions also include an estimate of expected rescission activity. Similar to our loss reserve estimates, our estimates for premium deficiency reserves could be adversely affected by several factors, including a deterioration of regional or economic conditions leading to a reduction in borrowers’ income and thus their ability to make mortgage payments, and a drop in housing values that could expose us to greater losses. Assumptions used in calculating the deficiency reserves can also be affected by volatility in the current housing and mortgage lending industries. To the extent premium patterns and actual loss experience differ from the assumptions used in calculating the premium deficiency reserves, the differences between the actual results and our estimates will affect future period earnings and could be material.

Premium Deficiency Reserve

Beginning in 2007, when we stopped writing Wall Street Bulk business, we began to separately measure the performance of these transactions and establish a premium deficiency reserve related to this business. The premium deficiency reserve reflects the present value of expected future losses and expenses that exceed the present value of expected future premiums and established loss reserves. Each quarter, we re-estimate the premium deficiency reserve on the remaining Wall Street bulk insurance in force. The premium deficiency reserve primarily changes from quarter to quarter as a result of two factors. First, it changes as the actual premiums, losses and expenses that were previously estimated are recognized. Each period such items are reflected in our financial statements as earned premium, losses incurred and expenses. The difference between the amount and timing of actual earned premiums, losses incurred and expenses and our previous estimates used to establish the premium deficiency reserves has an effect (either positive or negative) on that period’s results. Second, the premium deficiency reserve changes as our assumptions relating to the present value of expected future premiums, losses and expenses on the remaining Wall Street bulk insurance in force change. Changes to these assumptions also have an effect on that period’s results.

The decreases in the premium deficiency reserve for the years ended December 31, 2015, 2014 and 2013 were $24 million, $24 million, and $26 million, respectively. As of December 31, 2015, there was no premium deficiency reserve required. The decreases represent the net result of actual premiums, losses and expenses as well as a net change in assumptions for these periods. The change in assumptions for 2014 and 2013 are primarily related to higher estimated ultimate premiums resulting principally from an increase in the projected persistency rate, offset in part by higher estimated ultimate losses resulting principally from an increase in the number of projected claims that will ultimately be paid.

The calculation of premium deficiency reserves requires the use of significant judgments and estimates to determine the present value of future premium and present value of expected losses and expenses on our business. The calculation of future premium depends on, among other things, assumptions about persistency and repayment patterns on underlying loans. The calculation of expected losses and expenses depends on assumptions relating to severity of claims and claim rates on current defaults, and expected defaults in future periods. These assumptions also include an estimate of expected rescission activity. Similar to our loss reserve estimates, our estimates for premium deficiency reserves could be adversely affected by several factors, including a deterioration of regional or economic conditions leading to a reduction in borrowers’ income and thus their ability to make mortgage payments, and a drop in housing values that could expose us to greater losses. Assumptions used in calculating the deficiency reserves can also be affected by volatility in the current housing and mortgage lending industries. To the extent premium patterns and actual loss experience differ from the assumptions used in calculating the premium deficiency reserves, the differences between the actual results and our estimates will affect future period earnings and could be material.