Stockholders' Equity - Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Components of accumulated other comprehensive income/(loss)
Beginning balance	$ 2,542,848	$ 2,524,802
OCI before reclassifications	(3,722)	(3,620)
Amounts reclassified from AOCI	0	0
Other Comprehensive (Loss)	(3,722)	(3,620)
Ending balance	2,348,955	2,542,266
Total  AOCI
Components of accumulated other comprehensive income/(loss)
Beginning balance	45,578	77,293
Ending balance	41,856	73,673
Net Unrealized Gain/(Loss) on AFS Securities
Components of accumulated other comprehensive income/(loss)
Beginning balance	46,833	79,607
OCI before reclassifications	(4,977)	(3,855)
Amounts reclassified from AOCI	0	0
Other Comprehensive (Loss)	(4,977)	(3,855)
Ending balance	41,856	75,752
Net Unrealized Gain/(Loss) on Financing Agreements
Components of accumulated other comprehensive income/(loss)
Beginning balance	(1,255)	(2,314)
OCI before reclassifications	1,255	235
Amounts reclassified from AOCI	0	0
Other Comprehensive (Loss)	1,255	235
Ending balance	$ 0	$ (2,079)