Summary of Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Certain disclosures included in our Annual Report on Form 10-K are not required to be included on an interim basis in our quarterly reports on Form 10-Q. We have condensed or omitted these disclosures. Therefore, this Form 10-Q should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2020.
Consolidation	Our condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America ("U.S. GAAP") and consolidate the financial statements of the Company and our controlled subsidiaries. All significant intercompany transactions, balances, revenues and expenses are eliminated upon consolidation. In the opinion of management, the condensed consolidated financial statements reflect all adjustments, consisting of normal recurring accruals, which are necessary for a fair statement of our financial condition and results of operations for the periods presented.
Use of Estimates	The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in our condensed consolidated financial statements and accompanying notes. Examples of estimates include, but are not limited to, estimates of the fair values of financial instruments, interest income on mortgage-backed and credit risk transfer securities and allowances for credit losses. Actual results may differ from those estimates.
Accounting Pronouncements Recently Issued	Accounting Pronouncements Recently IssuedIn January 2021, the Financial Accounting Standards Board expanded existing accounting guidance for evaluating the effects of reference rate reform on financial reporting. The new guidance expands the temporary optional expedients and exceptions to U.S. GAAP for contract modifications, hedge accounting and other relationships that reference London Interbank Overnight Financing Rate ("LIBOR") to apply to all derivative instruments affected by the market-wide change in the interest rates used for discounting, margining or contract price alignment (commonly referred to as the discounting transition). The guidance can be applied as of January 1, 2020.

Our condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America ("U.S. GAAP") and consolidate the financial statements of the Company and our controlled subsidiaries. All significant intercompany transactions, balances, revenues and expenses are eliminated upon consolidation. In the opinion of management, the condensed consolidated financial statements reflect all adjustments, consisting of normal recurring accruals, which are necessary for a fair statement of our financial condition and results of operations for the periods presented.

Accounting Pronouncements Recently Issued

Accounting Pronouncements Recently IssuedIn January 2021, the Financial Accounting Standards Board expanded existing accounting guidance for evaluating the effects of reference rate reform on financial reporting. The new guidance expands the temporary optional expedients and exceptions to U.S. GAAP for contract modifications, hedge accounting and other relationships that reference London Interbank Overnight Financing Rate ("LIBOR") to apply to all derivative instruments affected by the market-wide change in the interest rates used for discounting, margining or contract price alignment (commonly referred to as the discounting transition). The guidance can be applied as of January 1, 2020.