Stockholders' Equity (Accumulated Other Comprehensive Income/(Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Components of accumulated other comprehensive income/(loss)
OCI before reclassifications	$ 4,302		$ 14,156	$ (29,055)
Amounts reclassified from AOCI	(7,114)	$ (5,178)	(22,660)	(15,458)
Other Comprehensive Income/(Loss)	(2,812)	(18,019)	(8,504)	(44,513)
Total AOCI
Components of accumulated other comprehensive income/(loss)
Balance at beginning of period	414,596	582,730	420,288	609,224
OCI before reclassifications		(12,841)
Amounts reclassified from AOCI		(5,178)
Other Comprehensive Income/(Loss)		(18,019)
Balance at end of period	411,784	564,711	411,784	564,711
Net Unrealized Gain/(Loss) on AFS Securities
Components of accumulated other comprehensive income/(loss)
Balance at beginning of period	422,261	574,485	417,167	620,648
OCI before reclassifications	24,008	(20,756)	44,307	(56,639)
Amounts reclassified from AOCI	(6,371)	(5,178)	(21,576)	(15,458)
Other Comprehensive Income/(Loss)	17,637	(25,934)	22,731	(72,097)
Balance at end of period	439,898	548,551	439,898	548,551
Net (Loss)/Gain on Swaps
Components of accumulated other comprehensive income/(loss)
Balance at beginning of period	(7,665)	8,245	3,121	(11,424)
OCI before reclassifications	(19,706)	7,915	(30,151)	27,584
Amounts reclassified from AOCI	(743)	0	(1,084)	0
Other Comprehensive Income/(Loss)	(20,449)	7,915	(31,235)	27,584
Balance at end of period	$ (28,114)	$ 16,160	$ (28,114)	$ 16,160