Repurchase Agreements - Repurchase Agreements by Maturity Period (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2022	Jun. 30, 2021	Dec. 31, 2021
Assets Sold under Agreements to Repurchase [Line Items]
Haircut percentage	2.75%		3.45%
Balance	$ 6,440,004		$ 3,948,037
Weighted Average Contractual Rate	0.34%		0.12%
Weighted Average Maturity in days	16 days	29 days
Agency Securities
Assets Sold under Agreements to Repurchase [Line Items]
Balance	$ 5,360,046		$ 3,849,037
Weighted Average Contractual Rate	0.37%		0.13%
Weighted Average Maturity in days	19 days	29 days
Agency Securities | Within 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Balance	$ 4,415,600		$ 2,565,743
Weighted Average Contractual Rate	0.37%		0.13%
Weighted Average Maturity in days	15 days	13 days
Agency Securities | 31 days to 60 days
Assets Sold under Agreements to Repurchase [Line Items]
Balance			$ 647,584
Weighted Average Contractual Rate			0.13%
Weighted Average Maturity in days		35 days
Agency Securities | 31 days to 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Balance	$ 917,841
Weighted Average Contractual Rate	0.40%
Weighted Average Maturity in days	34 days
Agency Securities | Maturity 61 To 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Balance			$ 635,710
Weighted Average Contractual Rate			0.11%
Weighted Average Maturity in days			89 days
Agency Securities | Greater than 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Balance	$ 26,605
Weighted Average Contractual Rate	0.98%
Weighted Average Maturity in days	175 days
U.S. Treasuries | Within 30 days
Assets Sold under Agreements to Repurchase [Line Items]
Balance	$ 1,079,958		$ 99,000
Weighted Average Contractual Rate	0.18%		0.12%
Weighted Average Maturity in days	1 day		3 days