Summary of Significant Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial statements include our accounts and those of our consolidated subsidiaries. All intercompany amounts have been eliminated. The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America ("GAAP") requires us 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 periods. Our most significant estimates include loan loss allowances. Actual results could differ from those estimates. These unaudited condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2019 ("Annual Report"), as filed with the Securities and Exchange Commission (the "SEC"). In the opinion of management, all adjustments (consisting only of normal recurring adjustments) necessary to present fairly our financial position, results of operations and cash flows have been included. Our results of operations for the three and six months ended June 30, 2020 are not necessarily indicative of the results to be expected for the full year or any other future period. We currently operate in one reporting segment. Risks and Uncertainties During the first quarter of 2020, there was a global outbreak of a novel coronavirus ("COVID-19"), which was declared by the World Health Organization as a pandemic. In response to COVID-19, the United States and numerous other countries have declared national emergencies, which has led to large scale quarantines as well as restrictions to business deemed non-essential. These responses to COVID-19 have disrupted economic activities and could have a continued significant adverse effect on economic and market conditions. As we are still in the midst of the COVID-19 pandemic we are not in a position to estimate the ultimate impact this will have on our business and the economy as a whole. We believe the estimates used in preparing our financial statements and related footnotes are reasonable and supportable based on the best information available to us as of June 30, 2020. The uncertainty surrounding COVID-19 may materially impact the accuracy of the estimates and assumptions used in the financial statements and related footnotes and, as a result, actual results may vary significantly from estimates. Current Expected Credit Losses ("CECL") In June 2016, the FASB issued ASU 2016-13 "Financial Instruments - Credit Losses (Topic 326) - Measurement of Credit Losses on Financial Instruments" ("ASU 2016-13"), which we refer to as the "CECL Standard." This update has changed how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value. The CECL Standard replaced the "incurred loss" approach under existing guidance with an "expected loss" model for instruments measured at amortized cost. The CECL Standard requires entities to record allowances for held-to-maturity debt securities that are deducted from the carrying amount of the assets to present the net carrying value at the amounts expected to be collected on the assets. We continue to record loan specific allowances as a practical expedient under the CECL Standard ("Specific CECL Allowance"), which we apply to assets that are collateral dependent and where the borrower or sponsor is experiencing financial difficulty. In addition, we now record a general allowance in accordance with the CECL Standard on the remainder of the loan portfolio ("General CECL Allowance", and together with the Specific CECL Allowance, "CECL Allowances") on a collective basis by assets with similar risk characteristics. The CECL Standard requires us to record an allowance for credit losses that are deducted from the carrying amount of our loan portfolio to present the net carrying value at the amounts expected to be collected on the assets. We adopted the CECL Standard through a cumulative-effect adjustment to retained earnings on January 1, 2020. Subsequent changes to the General CECL Allowance are recognized through net income (loss) on our condensed consolidated statement of operations. The CECL Standard requires an entity to consider historical loss experience, current conditions, and a reasonable and supportable forecast of the macroeconomic environment. The FASB recognizes what is known as the weighted average remaining maturity ("WARM") method as an acceptable approach for computing current expected credit losses. We have adopted the WARM method to comply with the CECL Standard in determining a General CECL Allowance for a majority of our portfolio. In the future, we may use other acceptable methods, such as a probability-of-default/loss-given-default method. For loans where we have deemed the borrower/sponsor to be experiencing financial difficulty, we have elected to apply a practical expedient in which the fair value of the underlying collateral is compared to the amortized cost of the loan in determining a Specific CECL Allowance. In accordance with the WARM method, an annual historical loss rate is applied to the amortized cost of an asset or pool of assets over the remaining expected life. The WARM method requires consideration of the timing of expected future fundings of existing commitments and repayments over each asset’s remaining life. An annual loss factor, adjusted for macroeconomic estimates, is applied over each subsequent period and aggregated to arrive at the General CECL Allowance. In determining the General CECL Allowance, we considered various factors including (i) historical loss experience in the commercial real estate lending market, (ii) timing of expected repayments and satisfactions, (iii) expected future funding, (iv) capital subordinate to us when we are the senior lender, (v) capital senior to us when we are the subordinate lender, and (vi) our current and future view of the macroeconomic environment. The standard requires the use of significant judgment to arrive at an estimated credit loss. There is significant uncertainty related to future macroeconomic conditions as the result of COVID-19. We derived an annual historical loss rate based on a commercial mortgage backed securities ("CMBS") database with historical losses from 1998 to the first quarter of 2020 provided by a third party, Trepp LLC. We applied various filters to arrive at a CMBS dataset most analogous to our current portfolio from which to determine an appropriate historical loss rate. The annual historical loss rate was further adjusted to reflect our expectations of the macroeconomic environment for a reasonable and supportable forecast period which we have determined to be one year. The General CECL Allowance on subordinate loans is calculated by incorporating both the loan balance of the position(s) of the structurally senior third-party lender(s) and the balance of our subordinate loan. The subordinate loan, by virtue of being the first loss position, is required to absorb losses prior to the senior position(s) being impacted, resulting in a higher percentage allowance attributable to the subordinate loan. The General CECL Allowance on unfunded loan commitments is time-weighted based on our expected commitment to fund such obligations. The General CECL Allowance on unfunded commitments is recorded as a liability on the condensed consolidated balance sheet within accounts payable, accrued expenses and other liabilities. At adoption, the General CECL Allowance was $30.9 million and was recorded in the condensed consolidated statement of changes in stockholders’ equity. Refer to Note 4 - Commercial Mortgage, Subordinate Loans and Other Lending Assets for further information regarding CECL. Secured Debt Arrangements Secured debt arrangements are accounted for as financing transactions, unless they meet the criteria for sale accounting. Loans financed through a secured debt arrangement remain on our balance sheet as an asset and cash received from the purchaser is recorded on our condensed consolidated balance sheet as a liability. Interest incurred in accordance with secured debt arrangements is recorded as interest expense. During the second quarter 2020, we entered into a private securitization with Barclays Bank, plc (the "Barclays Private Securitization"). We have determined that the issuer of this securitization, ACRE Debt 2 PLC, is a Variable Interest Entity ("VIE") of which we were deemed to be the primary beneficiary and therefore, we consolidated the operations of this entity for GAAP. The collateral assets of the securitization are included in commercial mortgage loans, net on our condensed consolidated balance sheet. The liabilities of the securitization to the senior noteholders, excluding the notes held by us, are included in secured debt arrangements, net on our condensed consolidated balance sheet.