Stockholders' Equity (Accumulated Other Comprehensive Income/(Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Components of accumulated other comprehensive income/(loss)
OCI before reclassifications	$ 5,250		$ 19,701	$ (57,276)
Amounts reclassified from AOCI	(15,184)	$ (9,455)	(38,139)	(25,580)
Other Comprehensive Income/(Loss)	(9,934)	(38,343)	(18,438)	(82,856)
Total AOCI
Components of accumulated other comprehensive income/(loss)
Balance at beginning of period	411,784	564,711	420,288	609,224
OCI before reclassifications		(28,888)
Amounts reclassified from AOCI		(9,455)
Other Comprehensive Income/(Loss)		(38,343)
Balance at end of period	401,850	526,368	401,850	526,368
Net Unrealized Gain/(Loss) on AFS Securities
Components of accumulated other comprehensive income/(loss)
Balance at beginning of period	439,898	548,551	417,167	620,648
OCI before reclassifications	5,483	(34,278)	50,085	(90,250)
Amounts reclassified from AOCI	(14,499)	(9,455)	(36,370)	(25,580)
Other Comprehensive Income/(Loss)	(9,016)	(43,733)	13,715	(115,830)
Balance at end of period	430,882	504,818	430,882	504,818
Net (Loss)/Gain on Swaps
Components of accumulated other comprehensive income/(loss)
Balance at beginning of period	(28,114)	16,160	3,121	(11,424)
OCI before reclassifications	(233)	5,390	(30,384)	32,974
Amounts reclassified from AOCI	(685)	0	(1,769)	0
Other Comprehensive Income/(Loss)	(918)	5,390	(32,153)	32,974
Balance at end of period	$ (29,032)	$ 21,550	$ (29,032)	$ 21,550