Concentrations of Credit Risk (Details) - Fannie Mae DUS and Freddie Mac TAH Loans - Liabilities - Credit Concentration Risk - USD ($) $ in Billions	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
California
Concentration Risk [Line Items]
Concentration risk percentage	21.00%	21.00%
Texas
Concentration Risk [Line Items]
Concentration risk percentage	15.00%	16.00%
Maximum pre-credit enhancement loss exposure	$ 6.1	$ 5.8

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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