CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Cash Flows From Operating Activities:
Net (Loss) Income		$ (943,398)	$ 54,464
Adjustments to reconcile net income to net cash used in operating activities:
Amortization of premiums, discounts, and securities issuance costs, net		(596)	(689)
Depreciation and amortization of non-financial assets		4,677	343
Originations of held-for-sale loans		(280,076)	(28,968)
Purchases of held-for-sale loans		(2,665,447)	(989,977)
Proceeds from sales of held-for-sale loans		2,733,285	851,331
Principal payments on held-for-sale loans		19,778	17,450
Net settlements of derivatives		(163,442)	(9,305)
Non-cash equity award compensation expense		3,188	3,090
Goodwill impairment expense		88,675	0
Market valuation adjustments		912,477	(31,439)
Realized gains, net		(3,852)	(10,686)
Net change in:
Accrued interest receivable and other assets		107,740	(50,006)
Accrued interest payable and accrued expenses and other liabilities		(54,414)	(12,119)
Net cash used in operating activities		(241,405)	(206,511)
Cash Flows From Investing Activities:
Originations of loans held-for-investment		(206,634)	(7,000)
Purchases of loans held-for-investment		0	(49,489)
Principal payments on loans held-for-investment		638,508	246,964
Purchases of real estate securities		(52,259)	(154,871)
Sales of multifamily securities held in consolidated securitization trusts		121,000	0
Proceeds from sales of real estate securities		529,494	74,018
Principal payments on real estate securities		11,952	24,498
Purchases of servicer advance investments		(158,618)	(68,976)
Principal repayments from servicer advance investments		22,815	66,532
Acquisition of 5 Arches, net of cash acquired		0	(3,714)
Net investment in participation in loan warehouse facility		0	38,209
Net investment in multifamily loan fund		24,842	(22,316)
Other investing activities, net		(20,514)	(3,295)
Net cash provided by investing activities		910,586	140,560
Cash Flows From Financing Activities:
Proceeds from borrowings on short-term debt		2,972,646	1,217,915
Repayments on short-term debt		(2,960,444)	(1,459,648)
Proceeds from issuance of asset-backed securities		377,164	330,534
Repayments on asset-backed securities issued		(363,696)	(163,146)
Proceeds from issuance of long-term debt		133,961	0
Repayments on long-term debt		(633,448)	0
Net settlements of derivatives		(84,336)	(35)
Net proceeds from issuance of common stock		2,262	182,512
Taxes paid on equity award distributions		(2,632)	(2,033)
Dividends paid		0	(29,774)
Other financing activities, net		3,497	0
Net cash (used in) provided by financing activities		(556,029)	76,325
Net increase in cash, cash equivalents and restricted cash		113,152	10,374
Cash, cash equivalents and restricted cash at beginning of period	[1]	290,833	205,077	$ 205,077
Cash, cash equivalents, and restricted cash at end of period	[1]	403,985	215,451	290,833	$ 205,077
Cash paid during the period for:
Interest		170,884	99,686
Taxes		109	77
Supplemental Noncash Information:
Real estate securities retained from loan securitizations		46,560	2,601
Retention of mortgage servicing rights from loan securitizations and sales				0	$ 223
Deconsolidation of multifamily loans held in securitization trusts		(3,849,779)	0
Deconsolidation of multifamily ABS		(3,706,789)	0
Transfers from loans held-for-sale to loans held-for-investment		382,635	389,486
Transfers from loans held-for-investment to loans held-for-sale		1,857,781	22,758
Transfers from residential loans to real estate owned		6,363	5,035
Right-of-use asset obtained in exchange for operating lease liability		5,362	12,661
Accrued but unpaid dividends		$ 37,800	$ 0	$ 0

[1] Cash, cash equivalents, and restricted cash at March 31, 2020 includes cash and cash equivalents of $378 million and restricted cash of $26 million, and at December 31, 2019 includes cash and cash equivalents of $197 million and restricted cash of $94 million.