Organization and Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Description of management fee	In exchange for these services, our Manager receives a management fee, paid monthly in arrears, in an amount equal to one-twelfth of 1.20% of our Equity (as defined in the Management Agreement).
Annual management fee as a percent of equity	1.20%
Building Estimated Useful Life	27 years 6 months
Building Salvage Value	$ 0
Unrecognized tax benefits	0
Unrecognized tax benefits, accrued interest or penalties	$ 0
Variable Interest Entities Primary Beneficiary
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Balance at end of period		$ 175,000
Accounting Standards Update 2016-13 | Adjustment
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Cumulative effect on retained earnings, net of tax		$ (30,000)
Minimum | Agency MBS
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
MBS initial fixed interest rate required, period	1 year
Maximum | Interest rate swap agreements
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Interest rate term for interest rate swap agreements	10 years
Maximum | Agency MBS
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
MBS initial fixed interest rate required, period	10 years