Commercial Mortgage Loans, Subordinate Loans and Other Lending Assets, Net - Allocation of Carrying Value of Loan Portfolio Based on Internal Risk Ratings (Details) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2023 USD ($) loan	Dec. 31, 2022 USD ($) loan
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	49	61
Total	$ 8,001,336	$ 8,708,214
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	100.00%	100.00%
Year 1	$ 169,707	$ 2,575,455
Year 2	2,610,749	2,462,499
Year 3	2,271,332	687,329
Year 4	542,838	1,637,050
Year 5	1,540,913	499,720
Prior	865,798	846,161
General CECL Allowance	(27,305)	(26,224)
Total carrying value, net	$ 7,974,031	$ 8,681,990
Weighted Average Risk Rating	3.1	3.0
Gross write-offs	$ 81,890	$ 7,000
Off-balance-sheet, credit loss, liability, amount excluded	$ 4,000	$ 4,300
1
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	0	0
Total	$ 0	$ 0
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	0.00%	0.00%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	0	0
Prior	$ 0	$ 0
2
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	3	2
Total	$ 192,291	$ 65,943
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	2.40%	0.80%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	126,658	0
Prior	$ 65,633	$ 65,943
3
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	42	54
Total	$ 7,452,050	$ 8,401,925
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	93.10%	96.50%
Year 1	$ 169,707	$ 2,575,455
Year 2	2,610,749	2,462,499
Year 3	2,271,332	687,329
Year 4	372,957	1,637,050
Year 5	1,414,255	479,769
Prior	$ 613,051	$ 559,823
4
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	2	2
Total	$ 88,312	$ 27,451
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	1.10%	0.30%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	0	19,951
Prior	$ 88,312	$ 7,500
5
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	2	3
Total	$ 268,683	$ 212,895
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	3.40%	2.40%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	169,881	0
Year 5	0	0
Prior	$ 98,802	$ 212,895

Loans And Leases Receivable, Number Of Contracts

No definition available.

Name:	ari_LoansAndLeasesReceivableNumberOfContracts
Namespace Prefix:	ari_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Loans And Leases Receivable, Weighted-Average Risk Rating

+ References

No definition available.

+ Details

Name:	ari_LoansAndLeasesReceivableWeightedAverageRiskRating
Namespace Prefix:	ari_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Mortgage Loans on Real Estate, Commercial and Consumer, Percentage of Portfolio

+ References

No definition available.

+ Details

Name:	ari_MortgageLoansOnRealEstateCommercialAndConsumerPercentageOfPortfolio
Namespace Prefix:	ari_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Off-Balance-Sheet, Credit Loss, Liability, Amount Excluded

+ References

No definition available.

+ Details

Name:	ari_OffBalanceSheetCreditLossLiabilityAmountExcluded
Namespace Prefix:	ari_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The reserve to cover probable credit losses related to specifically identified fixed maturity real estate loans as well as probable credit losses inherent in the remainder of that loan portfolio.

+ References

No definition available.

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-5

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479294/326-20-55-79

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-6

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated in current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-5

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479294/326-20-55-79

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

+ Details

Name:	us-gaap_MortgageLoansOnRealEstateCommercialAndConsumerNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_PassMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SpecialMentionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SubstandardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_DoubtfulMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_UnlikelyToBeCollectedFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: