Fair Value of Financial Instruments - Carrying Value and Estimated Fair Value of Company's Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Participations sold	$ (27,064)	$ (34,974)
Commercial Mortgage Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Participations sold	(27,064)	(9,217)
Subordinate Mortgage Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Participations sold	0	(25,757)
Carrying Value
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cash and cash equivalents	343,106	325,498
Carrying Value \| Level III
Accounts, Notes, Loans and Financing Receivable [Line Items]
Secured debt arrangements, net	(4,150,268)	(3,436,672)
Participations sold	(27,064)	(34,974)
Debt related To real estate owned, held for sale	0	(33,000)
Carrying Value \| Level III \| Secured Debt
Accounts, Notes, Loans and Financing Receivable [Line Items]
Senior secured term loans, net	(768,325)	(483,465)
Carrying Value \| Level III \| Senior Notes
Accounts, Notes, Loans and Financing Receivable [Line Items]
Senior secured term loans, net	(494,051)	0
Carrying Value \| Level III \| 2022 Notes
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes	(343,117)	(340,361)
Carrying Value \| Level III \| 2023 Notes
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes	(226,862)	(225,293)
Carrying Value \| Level III \| Commercial Mortgage Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	7,012,312	5,451,084
Carrying Value \| Level III \| Subordinate Mortgage Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	844,948	1,045,893
Estimate of Fair Value Measurement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cash and cash equivalents	343,106	325,498
Estimate of Fair Value Measurement \| Level III
Accounts, Notes, Loans and Financing Receivable [Line Items]
Secured debt arrangements, net	(4,150,268)	(3,436,672)
Participations sold	(27,064)	(34,919)
Debt related To real estate owned, held for sale	0	(33,000)
Estimate of Fair Value Measurement \| Level III \| Secured Debt
Accounts, Notes, Loans and Financing Receivable [Line Items]
Senior secured term loans, net	(782,995)	(475,263)
Estimate of Fair Value Measurement \| Level III \| Senior Notes
Accounts, Notes, Loans and Financing Receivable [Line Items]
Senior secured term loans, net	(489,175)	0
Estimate of Fair Value Measurement \| Level III \| 2022 Notes
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes	(347,522)	(327,381)
Estimate of Fair Value Measurement \| Level III \| 2023 Notes
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes	(231,150)	(214,875)
Estimate of Fair Value Measurement \| Level III \| Commercial Mortgage Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	6,945,038	5,361,948
Estimate of Fair Value Measurement \| Level III \| Subordinate Mortgage Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 725,906	$ 1,027,582

Debt Related To Real Estate Owned, Held For Sale

No definition available.

Name:	ari_DebtRelatedToRealEstateOwnedHeldForSale
Namespace Prefix:	ari_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

No definition available.

+ Details

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

- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of contractual arrangement with a lender under which borrowings can be made up to a specific amount at any point in time.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of mortgage loans held-for-sale.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of notes payable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20,22)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Definition

The aggregate amount of the participation liability at the end of the accounting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377297&loc=d3e10013-112621

+ Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=ari_CommercialMortgagePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=ari_SubordinateMortgagePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=ari_TwoThousandTwentyTwoNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=ari_TwoThousandTwentyThreeNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: