Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5618551-113959

+ Details

Name:	us-gaap_DerivativeGainLossOnDerivativeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(h))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

Name:	us-gaap_GainLossOnSaleOfDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

+ Details

Name:	us-gaap_UnrealizedGainLossOnDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_GainLossOnDerivativeInstrumentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeForwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ari_InterestRateCapandSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateCapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ari_InterestRateSwapInstrumentOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ari_InterestRateSwapInstrumentTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Derivatives - Summary of Amounts Recognized on Consolidated Statements of Operations Related to Company's Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Jun. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivative instruments - unrealized interest rate swap			$ 41,028	$ 33,000
Gain (Loss) on Derivative Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on sale of derivatives	$ (75)	$ (564)	171	(39,207)
Foreign currency forward, net
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivative instruments - unrealized interest rate swap	32,376	(35,076)	40,857	18,356
Gain (loss) on sale of derivatives	32,947	(34,537)	39,653	32,959
Foreign currency forward, net \| Gain (Loss) on Derivative Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Realized (gain) loss on derivative instruments - interest rate swap realized	571	539	(1,204)	14,603
Interest rate cap and swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on sale of derivatives	(75)	(564)	171	(39,207)
Interest Rate Cap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative notional amount						$ 1,100
Interest Rate Cap \| Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative notional amount	500,000	500,000	500,000	500,000	$ 500,000
Interest Rate Cap \| Gain (Loss) on Derivative Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivative instruments - unrealized interest rate swap	(75)	(564)	171	174
Interest Rate Swap, Instrument One \| Gain (Loss) on Derivative Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivative instruments - unrealized interest rate swap	0	0	0	14,470
Interest Rate Swap, Instrument Two \| Gain (Loss) on Derivative Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Realized (gain) loss on derivative instruments - interest rate swap realized	0	0		(53,851)
Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on sale of derivatives					$ (53,900)
Interest Rate Swap \| Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative notional amount	$ 0	$ 0	$ 0	$ 0