Segment Information - Components of Corporate/Other (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Interest income	$ 121,982	$ 150,117	$ 450,009	$ 429,700
Interest expense	(100,411)	(116,604)	(349,748)	(332,100)
Net Interest Income	21,571	33,513	100,261	97,600
Investment fair value changes, net	107,047	11,444	(611,557)	34,741
Other	(97)	575	2,406	1,053
Realized gains, net	602	4,714	30,419	18,227
Total non-interest income (loss), net	166,930	30,029	(552,648)	107,792
General and administrative expenses	(27,630)	(24,899)	(84,832)	(70,722)
Loan acquisition costs	(2,158)	(1,916)	(7,716)	(5,507)
Other expenses	(7,788)	(2,531)	(104,286)	(6,021)
Net Income (Loss)	141,812	34,310	(636,142)	120,040
Corporate/ Other
Segment Reporting Information [Line Items]
Interest income	1,804	4,295	7,738	13,924
Interest expense	(4,309)	(3,452)	(12,622)	(11,548)
Net Interest Income	(2,505)	843	(4,884)	2,376
Investment fair value changes, net	(178)	(452)	(917)	(1,008)
Other	934	0	1,692	2,710
Realized gains, net	0	0	25,182	0
Total non-interest income (loss), net	756	(452)	25,957	1,702
General and administrative expenses	(12,998)	(12,614)	(37,724)	(37,440)
Loan acquisition costs	0	(113)	(7)	(128)
Other expenses	(135)	(236)	(581)	(725)
Net Income (Loss)	(14,882)	(12,572)	(17,239)	(34,215)
Corporate/ Other | Legacy Consolidated VIEs
Segment Reporting Information [Line Items]
Interest income	1,795	4,295	7,675	13,924
Interest expense	(1,058)	(3,452)	(5,098)	(11,548)
Net Interest Income	737	843	2,577	2,376
Investment fair value changes, net	(81)	(407)	(702)	(904)
Other	0	0	0	0
Realized gains, net			0	0
Total non-interest income (loss), net	(81)	(407)	(702)	(904)
General and administrative expenses	0	0	0	0
Loan acquisition costs	0	0	0	0
Other expenses	0	0	0	0
Net Income (Loss)	656	436	1,875	1,472
Corporate/ Other | Other
Segment Reporting Information [Line Items]
Interest income	9	0	63	0
Interest expense	(3,251)	0	(7,524)	0
Net Interest Income	(3,242)	0	(7,461)	0
Investment fair value changes, net	(97)	(45)	(215)	(104)
Other	934	0	1,692	2,710
Realized gains, net			25,182	0
Total non-interest income (loss), net	837	(45)	26,659	2,606
General and administrative expenses	(12,998)	(12,614)	(37,724)	(37,440)
Loan acquisition costs	0	(113)	(7)	(128)
Other expenses	(135)	(236)	(581)	(725)
Net Income (Loss)	$ (15,538)	$ (13,008)	$ (19,114)	$ (35,687)