CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Marketable securities pledged as collateral	$ 5,226,133,000	$ 4,439,583,000
Financing receivable, allowance for credit loss	$ 212,000	$ 0
Preferred Stock - par value (in USD per share)	$ 0.01	$ 0.01
Preferred Stock - shares authorized (in shares)	50,000,000	50,000,000
Common Stock - par value (in USD per share)	$ 0.01	$ 0.01
Common Stock - shares authorized (in shares)	67,000,000	67,000,000
Common Stock - shares issued (in shares)	48,460,626	38,710,916
Common Stock - shares outstanding (in shares)	48,460,626	38,710,916
Series B Preferred Stock | Preferred Stock
Preferred Stock - dividend rate stated percentage	7.75%	7.75%
Preferred Stock - shares issued (in shares)	4,465,414	4,537,634
Preferred Stock - shares outstanding (in shares)	4,465,414	4,537,634
Preferred Stock - liquidation preference value	$ 111,635,000	$ 113,441,000
Series C Preferred Stock | Preferred Stock
Preferred Stock - dividend rate stated percentage	7.50%	7.50%
Preferred Stock - shares issued (in shares)	7,681,211	7,816,470
Preferred Stock - shares outstanding (in shares)	7,681,211	7,816,470
Preferred Stock - liquidation preference value	$ 192,030,000	$ 195,412,000