CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income/(loss)	$ 87,210	$ 95,599	$ (725,207)	$ 277,496
Other Comprehensive Income/(Loss):
Unrealized gains on securities available-for-sale	15,082	5,483	408,585	50,085
Reclassification adjustment for MBS sales included in net income	(60)	(14,499)	(389,127)	(36,370)
Reclassification adjustment for impairments included in net income	0	0	(344,269)	0
Derivative hedging instrument fair value changes, net	0	(233)	(50,127)	(30,384)
Changes in fair value of financing agreements at fair value due to changes in instrument-specific credit risk	(22,652)	0	(22,652)	0
Reclassification adjustment for losses/(gains) related to hedging instruments included in net income	7,176	(685)	72,802	(1,769)
Other Comprehensive Income/(Loss)	(454)	(9,934)	(324,788)	(18,438)
Comprehensive income before preferred stock dividends	86,756	85,665	(1,049,995)	259,058
Dividends required on preferred stock	(8,219)	(3,750)	(21,578)	(11,250)
Comprehensive Income/(Loss) Available to Common Stock and Participating Securities	$ 78,537	$ 81,915	$ (1,071,573)	$ 247,808