Summary of Significant Accounting Policies (Repurchase Agreements) (Details)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Repurchase financing period, low end of range	1 month
Repurchase financing period, high end of range	6 months
Repurchase financings collateralized by residential whole loans, low end	3 months
Repurchase financings collateralized by residential whole loans, high end	12 months