Summary of the Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation and Consolidation and Statements of Financial Condition Presentation	Basis of Presentation and Consolidation The accompanying consolidated financial statements and related notes of the Company have been prepared in accordance with accounting principles generally accepted in the United States, or GAAP. In the opinion of the Company, all normal and recurring adjustments considered necessary for a fair presentation of its financial position, results of operations and cash flows have been included. Investment securities transactions are recorded on the trade date. Certain prior period amounts have been reclassified to conform to the current period's presentation. The consolidated financial statements include the Company’s accounts, the accounts of its wholly-owned subsidiaries, and variable interest entities, or VIEs, in which the Company is the primary beneficiary. All intercompany balances and transactions have been eliminated in consolidation. The Company uses securitization trusts considered to be VIEs in its securitization transactions. VIEs are defined as entities in which equity investors (i) do not have the characteristics of a controlling financial interest, or (ii) do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties. The entity that consolidates a VIE is known as its primary beneficiary and is generally the entity with (i) the power to direct the activities that most significantly impact the VIEs’ economic performance, and (ii) the right to receive benefits from the VIE or the obligation to absorb losses of the VIE that could be significant to the VIE. For VIEs that do not have substantial on-going activities, the power to direct the activities that most significantly impact the VIEs’ economic performance may be determined by an entity’s involvement with the design and structure of the VIE. The trusts are structured as entities that receive principal and interest on the underlying collateral and distribute those payments to the security holders. The assets held by the securitization entities are restricted in that they can only be used to fulfill the obligations of the securitization entity. The Company’s risks associated with its involvement with these VIEs are limited to its risks and rights as a holder of the security it has retained as well as certain risks associated with being the sponsor and depositor of and the seller, directly or indirectly to, the securitizations entities. Determining the primary beneficiary of a VIE requires judgment. The Company determined that for the securitizations it consolidates, its ownership provides the Company with the obligation to absorb losses or the right to receive benefits from the VIE that could be significant to the VIE. In addition, the Company has the power to direct the activities of the VIEs that most significantly impact the VIEs’ economic performance, or power, such as rights to replace the servicer without cause, or the Company was determined to have power in connection with its involvement with the structure and design of the VIE. The Company’s interest in the assets held by these securitization vehicles, which are consolidated on the Company’s Consolidated Statements of Financial Condition, is restricted by the structural provisions of these trusts, and a recovery of the Company’s investment in the vehicles will be limited by each entity’s distribution provisions. Generally, the securities retained by the Company are the most subordinate in the capital structure, which means those securities receive distributions after the senior securities have been paid. The liabilities of the securitization vehicles, which are also consolidated on the Company’s Consolidated Statements of Financial Condition, are non-recourse to the Company, and can only be satisfied using proceeds from each securitization vehicle’s respective asset pool. The assets of securitization entities are comprised of residential mortgage-backed securities (or RMBS), or residential mortgage loans.Statements of Financial Condition PresentationThe Company’s Consolidated Statements of Financial Condition include both the Company’s direct assets and liabilities and the assets and liabilities of consolidated securitization vehicles. Retained beneficial interests of the consolidated securitization vehicles are eliminated on consolidation. Assets of each consolidated VIE can only be used to satisfy the obligations of that VIE, and the liabilities of consolidated VIEs are non-recourse to the Company. The Company is not obligated to provide, nor does it intend to provide, any financial support to these consolidated securitization vehicles. The notes to the consolidated financial statements describe the Company’s assets and liabilities including the assets and liabilities of consolidated securitization vehicles.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Although the Company’s estimates contemplate current conditions and how it expects them to change in the future, it is reasonably possible that actual conditions could be materially different than anticipated in those estimates, which could have a material adverse impact on the Company’s results of operations and its financial condition. The Company has made significant estimates including in accounting for income recognition on Agency MBS, Non-Agency RMBS, IO MBS (Note 3) and residential mortgage loans (Note 4), valuation of Agency MBS and Non-Agency RMBS (Notes 3 and 5), residential mortgage loans (Note 4 and 5), securitized debt (Note 5 and 7) and derivative instruments (Notes 5 and 10). Actual results could differ materially from those estimates.
Significant Accounting Policies and Recent Accounting Pronouncements	Significant Accounting PoliciesThere have been no significant changes to the Company's accounting policies included in Note 2 to the consolidated financial statements of the Company’s Form 10-K for the year ended December 31, 2020, other than the significant accounting policies discussed below.Recent Accounting Pronouncements Reference Rate Reform (Topic 848) In March 2020, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) No. 2020-4, Reference Rate Reform: Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The amendments in this update provide optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The amendments in this update apply only to contracts, hedging relationships, and other transactions that reference London Inter Bank Offering Rate (or LIBOR) or another reference rate expected to be discontinued because of reference rate reform. The amendments in this update are effective for contracts held by the Company subject to reference rate reform that fall within the scope of this update beginning immediately through December 31, 2022 at which time the transition is expected to be complete. The Company has not yet had any contracts modified to adopt reference rate reform. When a contract within the scope of this update is updated for reference rate reform, the Company will evaluate the impact in accordance with this update. Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) In August 2020, the FASB issued ASU No. 2020-6, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity. The FASB issued this update to simplify the current guidance for convertible instruments and the derivatives scope exception for contracts in an entity’s own equity. Additionally, the amendments affect the diluted earnings per share, or EPS, calculation for instruments that may be settled in cash or shares and for convertible instruments. The update also provides for expanded disclosure requirements to increase transparency. The amendments in this update are effective for the Company on January 1, 2022. The Company has not yet adopted this guidance and is currently evaluating what impact this update will have on the consolidated financial statements.
Fair Value Disclosure	Fair Value Disclosure A complete discussion of the methodology utilized by the Company to estimate the fair value of its financial instruments is included in Note 5 to these consolidated financial statements.
Income Taxes	Income TaxesThe Company does not have any material unrecognized tax positions that would affect its financial statements or require disclosure.

Summary of the Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2021

Basis of Presentation and Consolidation and Statements of Financial Condition Presentation

Basis of Presentation and Consolidation

The accompanying consolidated financial statements and related notes of the Company have been prepared in accordance with accounting principles generally accepted in the United States, or GAAP. In the opinion of the Company, all normal and recurring adjustments considered necessary for a fair presentation of its financial position, results of operations and cash flows have been included. Investment securities transactions are recorded on the trade date. Certain prior period amounts have been reclassified to conform to the current period's presentation.

The consolidated financial statements include the Company’s accounts, the accounts of its wholly-owned subsidiaries, and variable interest entities, or VIEs, in which the Company is the primary beneficiary. All intercompany balances and transactions have been eliminated in consolidation.

The Company uses securitization trusts considered to be VIEs in its securitization transactions. VIEs are defined as entities in which equity investors (i) do not have the characteristics of a controlling financial interest, or (ii) do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties. The entity that consolidates a VIE is known as its primary beneficiary and is generally the entity with (i) the power to direct the activities that most significantly impact the VIEs’ economic performance, and (ii) the right to receive benefits from the VIE or the obligation to absorb losses of the VIE that could be significant to the VIE. For VIEs that do not have substantial on-going activities, the power to direct the activities that most significantly impact the VIEs’ economic performance may be determined by an entity’s involvement with the design and structure of the VIE.

The trusts are structured as entities that receive principal and interest on the underlying collateral and distribute those payments to the security holders. The assets held by the securitization entities are restricted in that they can only be used to fulfill the

obligations of the securitization entity. The Company’s risks associated with its involvement with these VIEs are limited to its risks and rights as a holder of the security it has retained as well as certain risks associated with being the sponsor and depositor of and the seller, directly or indirectly to, the securitizations entities.

Determining the primary beneficiary of a VIE requires judgment. The Company determined that for the securitizations it consolidates, its ownership provides the Company with the obligation to absorb losses or the right to receive benefits from the VIE that could be significant to the VIE. In addition, the Company has the power to direct the activities of the VIEs that most significantly impact the VIEs’ economic performance, or power, such as rights to replace the servicer without cause, or the Company was determined to have power in connection with its involvement with the structure and design of the VIE.

The Company’s interest in the assets held by these securitization vehicles, which are consolidated on the Company’s Consolidated Statements of Financial Condition, is restricted by the structural provisions of these trusts, and a recovery of the Company’s investment in the vehicles will be limited by each entity’s distribution provisions. Generally, the securities retained by the Company are the most subordinate in the capital structure, which means those securities receive distributions after the senior securities have been paid. The liabilities of the securitization vehicles, which are also consolidated on the Company’s Consolidated Statements of Financial Condition, are non-recourse to the Company, and can only be satisfied using proceeds from each securitization vehicle’s respective asset pool.

The assets of securitization entities are comprised of residential mortgage-backed securities (or RMBS), or residential mortgage loans.Statements of Financial Condition PresentationThe Company’s Consolidated Statements of Financial Condition include both the Company’s direct assets and liabilities and the assets and liabilities of consolidated securitization vehicles. Retained beneficial interests of the consolidated securitization vehicles are eliminated on consolidation. Assets of each consolidated VIE can only be used to satisfy the obligations of that VIE, and the liabilities of consolidated VIEs are non-recourse to the Company. The Company is not obligated to provide, nor does it intend to provide, any financial support to these consolidated securitization vehicles. The notes to the consolidated financial statements describe the Company’s assets and liabilities including the assets and liabilities of consolidated securitization vehicles.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Although the Company’s estimates contemplate current conditions and how it expects them to change in the future, it is reasonably possible that actual conditions could be materially different than anticipated in those estimates, which could have a material adverse impact on the Company’s results of operations and its financial condition.

The Company has made significant estimates including in accounting for income recognition on Agency MBS, Non-Agency RMBS, IO MBS (Note 3) and residential mortgage loans (Note 4), valuation of Agency MBS and Non-Agency RMBS (Notes 3 and 5), residential mortgage loans (Note 4 and 5), securitized debt (Note 5 and 7) and derivative instruments (Notes 5 and 10). Actual results could differ materially from those estimates.

Significant Accounting Policies and Recent Accounting Pronouncements

Significant Accounting PoliciesThere have been no significant changes to the Company's accounting policies included in Note 2 to the consolidated financial statements of the Company’s Form 10-K for the year ended December 31, 2020, other than the significant accounting policies discussed below.Recent Accounting Pronouncements

Reference Rate Reform (Topic 848)

In March 2020, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) No. 2020-4, Reference Rate Reform: Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The amendments in this update provide optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The amendments in this update apply only to contracts, hedging relationships, and other transactions that reference London Inter Bank Offering Rate (or LIBOR) or another reference rate expected to be discontinued because of reference rate reform. The amendments in this update are effective for contracts held by the Company subject to reference rate reform that fall within the scope of this update beginning immediately through December 31, 2022 at which time the transition is expected to be complete. The Company has not yet had any contracts modified to adopt reference rate reform. When a contract within the scope of this update is updated for reference rate reform, the Company will evaluate the impact in accordance with this update.

Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40)

In August 2020, the FASB issued ASU No. 2020-6, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity. The FASB issued this update to simplify the current guidance for convertible instruments and the derivatives scope exception for contracts in an entity’s own equity. Additionally, the amendments affect the diluted earnings per share, or EPS, calculation for instruments that may be settled in cash or shares and for convertible instruments. The update also provides for expanded disclosure requirements to increase transparency. The amendments in this update are effective for the Company on January 1, 2022. The Company has not yet adopted this guidance and is currently evaluating what impact this update will have on the consolidated financial statements.

Fair Value Disclosure

A complete discussion of the methodology utilized by the Company to estimate the fair value of its financial instruments is included in Note 5 to these consolidated financial statements.

Income Taxes

Income TaxesThe Company does not have any material unrecognized tax positions that would affect its financial statements or require disclosure.