Residential Mortgage Securities and MSR-Related Assets (MSR Related Assets - Narrative) (Details) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Term notes backed by MSR-related collateral
Debt Securities, Available-for-sale [Line Items]
Term notes backed by MSR related collateral	$ 224,782,000	$ 224,782,000	$ 1,157,463,000
Amortized costs	184,300,000	184,300,000	1,200,000,000
Gross unrealized gains	40,500,000	$ 40,500,000	$ 5,200,000
Weighted average yield		12.87%	4.75%
Weighted average to maturity		9 years 8 months 12 days	5 years 3 months 18 days
Proceeds from sale of MSR	574,900,000	$ 711,700,000
Realized losses	53,300,000	28,700,000
Impairment		280,800,000
Corporate Loan
Debt Securities, Available-for-sale [Line Items]
Commitment to lend				$ 100,000,000.0
Amount drawn	$ 31,800,000	$ 31,800,000
Interest coupon rate	5.26%	5.26%
Debt term		2 months
Commitment period on undrawn amount		2 months
Minimum | Corporate Loan
Debt Securities, Available-for-sale [Line Items]
Commitment fee on undrawn amount	0.25%	0.25%
Maximum | Corporate Loan
Debt Securities, Available-for-sale [Line Items]
Commitment fee on undrawn amount	1.00%	1.00%