Risk Management and Use of Derivative Financial Instruments - Derivative Gain Loss Recognized in Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Amount of Gain (Loss) on Derivatives Recognized in Income
Total	$ (1,116)	$ (1,313)	$ 790	$ (18)
Derivatives Not Designated as Hedging Instruments \| Foreign currency collars \| Non-operating income
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	(841)	(208)	159	431
Derivatives Not Designated as Hedging Instruments \| Stock warrants \| Other gains and (losses)
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	(500)	(1,400)	(500)	(1,300)
Derivatives Not Designated as Hedging Instruments \| Foreign currency forward contracts \| Non-operating income
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	0	(267)	0	(43)
Derivatives Not Designated as Hedging Instruments \| Interest rate swaps \| Interest expense
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	0	15	0	30
Derivatives in Cash Flow Hedging Relationships \| Interest rate swaps \| Interest expense
Amount of Gain (Loss) on Derivatives Recognized in Income
Gain (loss) on hedging activity	$ 225	$ 547	$ 1,131	$ 864

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4CC
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL109998890-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

+ References

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

+ Details

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

- Definition

Gain (loss) incurred in hedging activities.

+ References

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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