Short and Long-term Funding Remaining Contractual Maturity of Agreements (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Remaining Contractual Maturity of the Agreements
Repurchase agreements	$ 185,901	$ 71,097
Overnight and Continuous
Remaining Contractual Maturity of the Agreements
Repurchase agreements	185,901	71,097
Up to 30 days
Remaining Contractual Maturity of the Agreements
Repurchase agreements	0	0
30-90 days
Remaining Contractual Maturity of the Agreements
Repurchase agreements	0	0
Greater than 90 days
Remaining Contractual Maturity of the Agreements
Repurchase agreements	0	0
Agency mortgage-related securities
Remaining Contractual Maturity of the Agreements
Repurchase agreements	185,901	71,097
Agency mortgage-related securities | Overnight and Continuous
Remaining Contractual Maturity of the Agreements
Repurchase agreements	185,901	71,097
Agency mortgage-related securities | Up to 30 days
Remaining Contractual Maturity of the Agreements
Repurchase agreements	0	0
Agency mortgage-related securities | 30-90 days
Remaining Contractual Maturity of the Agreements
Repurchase agreements	0	0
Agency mortgage-related securities | Greater than 90 days
Remaining Contractual Maturity of the Agreements
Repurchase agreements	$ 0	$ 0