Equity - Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment fair value changes, net	$ 107,047	$ 11,444	$ (611,557)	$ 34,741
Realized gains, net	(602)	(4,714)	(30,419)	(18,227)
Interest expense	100,411	116,604	349,748	332,100
Net income before provision for income taxes	150,925	34,196	(649,221)	123,142
Reclassification out of Accumulated Other Comprehensive Income | Available-for-Sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment fair value changes, net	(444)	0	1,027	0
Realized gains, net	0	(3,492)	(12,552)	(15,807)
Net income before provision for income taxes	(444)	(3,492)	(11,525)	(15,807)
Reclassification out of Accumulated Other Comprehensive Income | Interest Rate Agreements Accounted for as Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	1,040	0	2,148	0
Net income before provision for income taxes	$ 1,040	$ 0	$ 2,148	$ 0