Segment Information - Components of Corporate/Other (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Interest income	$ 129,946	$ 148,542	$ 328,027	$ 279,583
Interest expense	(102,666)	(116,220)	(249,337)	(215,496)
Net Interest Income	27,280	32,322	78,690	64,087
Investment fair value changes, net	152,228	3,138	(718,604)	23,297
Realized gains, net	25,965	2,827	29,817	13,513
Total non-interest income (loss), net	173,376	29,984	(719,578)	77,763
General and administrative expenses	(30,092)	(26,255)	(62,760)	(49,414)
Other expenses	(5,083)	(2,452)	(96,498)	(3,490)
Net Income (Loss)	165,444	31,266	(777,954)	85,730
Corporate/ Other
Segment Reporting Information [Line Items]
Interest income	2,740	4,776	5,934	9,629
Interest expense	(5,791)	(3,981)	(8,313)	(8,096)
Net Interest Income	(3,051)	795	(2,379)	1,533
Investment fair value changes, net	(230)	(159)	(739)	(556)
Other income	758	0	758	2,710
Realized gains, net	25,182	0	25,182	0
Total non-interest income (loss), net	25,710	(159)	25,201	2,154
General and administrative expenses	(13,818)	(12,436)	(24,733)	(24,841)
Other expenses	(134)	(311)	(446)	(489)
Net Income (Loss)	8,707	(12,111)	(2,357)	(21,643)
Corporate/ Other | Legacy Consolidated VIEs
Segment Reporting Information [Line Items]
Interest income	2,686	4,776	5,880	9,629
Interest expense	(1,518)	(3,981)	(4,040)	(8,096)
Net Interest Income	1,168	795	1,840	1,533
Investment fair value changes, net	(230)	(123)	(621)	(497)
Other income	0	0	0	0
Realized gains, net	0	0	0	0
Total non-interest income (loss), net	(230)	(123)	(621)	(497)
General and administrative expenses	0	0	0	0
Other expenses	0	0	0	0
Net Income (Loss)	938	672	1,219	1,036
Corporate/ Other | Other
Segment Reporting Information [Line Items]
Interest income	54	0	54	0
Interest expense	(4,273)	0	(4,273)	0
Net Interest Income	(4,219)	0	(4,219)	0
Investment fair value changes, net	0	(36)	(118)	(59)
Other income	758	0	758	2,710
Realized gains, net	25,182	0	25,182	0
Total non-interest income (loss), net	25,940	(36)	25,822	2,651
General and administrative expenses	(13,818)	(12,436)	(24,733)	(24,841)
Other expenses	(134)	(311)	(446)	(489)
Net Income (Loss)	$ 7,769	$ (12,783)	$ (3,576)	$ (22,679)