Equity - Changes to Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Net unrealized gains (losses) on our Level 3 AFS securities	$ 52,000		$ (24,000)
Balance at beginning of period	725,202	$ 1,549,927	1,827,231	$ 1,348,794
Total other comprehensive income (loss)	56,140	(3,761)	(70,904)	(12,374)
Balance at End of Period	936,576	1,564,032	936,576	1,564,032
Net Unrealized Gains (Losses) on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(1,865)	92,567	92,452	95,342
Other comprehensive income (loss) before reclassifications	52,393	8,562	(28,126)	15,280
Amounts reclassified from other accumulated comprehensive income	2,718	(2,822)	(11,080)	(12,315)
Total other comprehensive income (loss)	55,111	5,740	(39,206)	2,965
Balance at End of Period	53,246	98,307	53,246	98,307
Net Unrealized Losses on Interest Rate Agreements Accounted for as Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(83,666)	(39,883)	(50,939)	(34,045)
Other comprehensive income (loss) before reclassifications	0	(9,501)	(32,806)	(15,339)
Amounts reclassified from other accumulated comprehensive income	1,029	0	1,108	0
Total other comprehensive income (loss)	1,029	(9,501)	(31,698)	(15,339)
Balance at End of Period	$ (82,637)	$ (49,384)	$ (82,637)	$ (49,384)