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, 2022	Dec. 31, 2021
Concentration Risk
Maximum DB Cayman credit protection	$ 7.9	$ 7.8
California
Concentration Risk
Concentration risk percentage	21.00%	20.00%
Texas
Concentration Risk
Concentration risk percentage	13.00%	13.00%

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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