Securities - Significant Assumptions (Details) - Non-agency residential	Mar. 31, 2019
Weighted Average
Significant Assumptions:
Prepayment speed	12.10%
Loss severity	20.50%
Life default rate	17.30%
Weighted Average \| Prime
Significant Assumptions:
Loss severity	15.80%
Life default rate	12.50%
Weighted Average \| Alt-A
Significant Assumptions:
Loss severity	16.10%
Life default rate	16.20%
Weighted Average \| Subprime
Significant Assumptions:
Loss severity	25.30%
Life default rate	20.60%
10th Percentile
Significant Assumptions:
Prepayment speed	3.00%
Loss severity	8.60%
Life default rate	1.20%
90th Percentile
Significant Assumptions:
Prepayment speed	21.00%
Loss severity	38.50%
Life default rate	65.60%