Securities - Significant Assumptions (Details) - Non-agency residential	Jun. 30, 2017
Weighted Average
Significant Assumptions:
Prepayment speed	11.50%
Loss severity	20.30%
Life default rate	22.00%
Weighted Average \| Prime
Significant Assumptions:
Loss severity	17.20%
Life default rate	15.80%
Weighted Average \| Alt-A
Significant Assumptions:
Loss severity	18.90%
Life default rate	22.80%
Weighted Average \| Subprime
Significant Assumptions:
Loss severity	30.40%
Life default rate	23.00%
10th Percentile
Significant Assumptions:
Prepayment speed	2.90%
Loss severity	9.20%
Life default rate	1.20%
90th Percentile
Significant Assumptions:
Prepayment speed	20.00%
Loss severity	37.40%
Life default rate	79.20%