Equity - Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment fair value changes, net	$ (588,438)	$ 35,500	$ (25,689)
Realized gains, net	(30,424)	(23,821)	(27,041)
Net income before provision for income taxes	(586,455)	176,623	130,688
Interest expense	448,005	479,808	$ 239,039
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains on Available-for-Sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment fair value changes, net	388	0
Realized gains, net	(12,553)	(19,967)
Net income before provision for income taxes	(12,165)	(19,967)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income before provision for income taxes	3,188	0
Interest expense	$ 3,188	$ 0