Stockholders' Equity (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Components of accumulated other comprehensive income/(loss)
Amounts reclassified from AOCI	$ 5,178	$ 6,274	$ 15,458	$ 16,634
Net OCI during the period	(18,019)	37,719	(44,513)	58,700
Net Unrealized Gain/(Loss) on AFS Securities
Components of accumulated other comprehensive income/(loss)
Balance at beginning of period	574,485	629,487	620,648	620,403
OCI before reclassifications	(20,756)	45,010	(56,639)	64,454
Amounts reclassified from AOCI	(5,178)	(6,274)	(15,458)	(16,634)
Net OCI during the period	(25,934)	38,736	(72,097)	47,820
Balance at end of period	548,551	668,223	548,551	668,223
Net (Loss)/Gain on Swaps
Components of accumulated other comprehensive income/(loss)
Balance at beginning of period	8,245	(34,824)	(11,424)	(46,721)
OCI before reclassifications	7,915	(1,017)	27,584	10,880
Amounts reclassified from AOCI	0	0	0	0
Net OCI during the period	7,915	(1,017)	27,584	10,880
Balance at end of period	16,160	(35,841)	16,160	(35,841)
Total AOCI
Components of accumulated other comprehensive income/(loss)
Balance at beginning of period	582,730	594,663	609,224	573,682
OCI before reclassifications	(12,841)	43,993	(29,055)	75,334
Amounts reclassified from AOCI	(5,178)	(6,274)	(15,458)	(16,634)
Net OCI during the period	(18,019)	37,719	(44,513)	58,700
Balance at end of period	$ 564,711	$ 632,382	$ 564,711	$ 632,382