Related Party Transactions - Schedule of Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Management fees	$ 31,108	$ 29,628	$ 29,571
Less management fees waived	(8,600)	(8,855)	0
US Treasury Securities
Related Party Transaction [Line Items]
U.S. Treasury Securities Purchased	987,887	4,621,776	1,685,058
ARRM
Related Party Transaction [Line Items]
Management fees	31,063	29,580	29,513
Less management fees waived	(8,600)	(8,855)	0
Total Management fee expense	22,463	20,725	29,513
BUCKLER Securities, LLC \| Corporate Joint Venture
Related Party Transaction [Line Items]
Repurchase agreements	1,963,679	2,998,111
Collateral posted on repurchase agreements	2,036,385	3,117,929
Interest on repurchase agreements	3,504	38,663	$ 120,090
BUCKLER Securities, LLC \| Corporate Joint Venture \| US Treasury Securities
Related Party Transaction [Line Items]
U.S. Treasury Securities Purchased	$ 100,000	$ 0

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Carrying amount as of the balance sheet date of obligations due all related parties.

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Amount of expenses related to the managing member or general partner for management of the day-to-day business functions of the limited liability company (LLC) or limited partnership (LP).

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Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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