Debt - Schedule of Repurchase Facilities (Details)		3 Months Ended	12 Months Ended
	Sep. 13, 2019 extension	Mar. 31, 2020 USD ($) extension	Dec. 31, 2019 USD ($) extension	Sep. 03, 2019 USD ($)	Sep. 02, 2019 USD ($)
Assets Sold under Agreements to Repurchase [Line Items]
Committed Financing		$ 1,175,000,000	$ 1,275,000,000
Amount Outstanding		234,524,000	252,543,000
Interest expense		$ 3,642,000	$ 16,616,000
USB Repo Facility
Assets Sold under Agreements to Repurchase [Line Items]
Number of extension options | extension		2	2
Extension on initial maturity date		1 year	1 year
WF Repo Facility
Assets Sold under Agreements to Repurchase [Line Items]
Number of extension options | extension	1	3	3
Extension on initial maturity date	1 year	1 year	1 year
Barclays Revolver Facility
Assets Sold under Agreements to Repurchase [Line Items]
Number of extension options | extension	1
Extension on initial maturity date	1 year
Barclays Repo Facility
Assets Sold under Agreements to Repurchase [Line Items]
Number of extension options | extension		2	2
Extension on initial maturity date		1 year	1 year
Secured Debt | Barclays Repo Facility
Assets Sold under Agreements to Repurchase [Line Items]
Committed Financing		$ 300,000,000	$ 300,000,000
Amount Outstanding		30,730,000	32,700,000
Interest expense		$ 332,000	$ 1,260,000
Ending Weighted Average Interest Rate		3.24%	3.80%
Revolving Credit Facility
Assets Sold under Agreements to Repurchase [Line Items]
Amount Outstanding		$ 496,880,000	$ 394,359,000
Ending Weighted Average Interest Rate		2.33%	2.79%
Revolving Credit Facility | JPM Repo Facility
Assets Sold under Agreements to Repurchase [Line Items]
Committed Financing		$ 300,000,000	$ 300,000,000	$ 300,000,000	$ 520,000,000
Amount Outstanding		119,604,000	107,526,000
Interest expense		$ 1,362,000	$ 6,862,000
Ending Weighted Average Interest Rate		3.83%	4.51%
Revolving Credit Facility | USB Repo Facility
Assets Sold under Agreements to Repurchase [Line Items]
Committed Financing		$ 100,000,000	$ 100,000,000
Amount Outstanding		8,250,000	0
Interest expense		$ 152,000	622,000
Ending Weighted Average Interest Rate		3.18%
Revolving Credit Facility | CS Repo Facility
Assets Sold under Agreements to Repurchase [Line Items]
Committed Financing		$ 200,000,000	300,000,000
Amount Outstanding		71,740,000	87,375,000
Interest expense		$ 1,349,000	$ 5,563,000
Ending Weighted Average Interest Rate		4.06%	4.84%
Revolving Credit Facility | WF Repo Facility
Assets Sold under Agreements to Repurchase [Line Items]
Committed Financing		$ 175,000,000	$ 175,000,000
Amount Outstanding		0	24,942,000
Interest expense		396,000	$ 1,333,000
Ending Weighted Average Interest Rate			3.65%
Revolving Credit Facility | Secured Debt | Barclays Revolver Facility
Assets Sold under Agreements to Repurchase [Line Items]
Committed Financing		100,000,000	$ 100,000,000
Amount Outstanding		4,200,000	0
Interest expense		$ 51,000	$ 976,000
Ending Weighted Average Interest Rate		5.34%