Securities - Significant Assumptions (Details) - Non-agency residential	Dec. 31, 2016
Weighted Average
Significant Assumptions:
Prepayment speed	13.80%
Loss severity	20.10%
Life default rate	20.40%
Weighted Average \| Prime
Significant Assumptions:
Loss severity	17.00%
Life default rate	13.90%
Weighted Average \| Alt-A
Significant Assumptions:
Loss severity	18.80%
Life default rate	21.70%
Weighted Average \| Subprime
Significant Assumptions:
Loss severity	30.40%
Life default rate	20.90%
10th Percentile
Significant Assumptions:
Prepayment speed	4.60%
Loss severity	8.80%
Life default rate	0.70%
90th Percentile
Significant Assumptions:
Prepayment speed	27.00%
Loss severity	36.50%
Life default rate	77.40%