Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ 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(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Borrower And Guarantor Obligations Under Debt Agreement, Capital Stock Of First-tier Foreign Subsidiaries, Percent

+ References

No definition available.

+ Details

Name:	w_BorrowerAndGuarantorObligationsUnderDebtAgreementCapitalStockOfFirsttierForeignSubsidiariesPercent
Namespace Prefix:	w_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Applicable Margin

+ References

No definition available.

+ Details

Name:	w_DebtInstrumentApplicableMargin
Namespace Prefix:	w_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Revolving Credit Facility Future Increase Available to Borrowing Capacity

+ References

No definition available.

+ Details

Name:	w_RevolvingCreditFacilityFutureIncreaseAvailabletoBorrowingCapacity
Namespace Prefix:	w_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsEffectiveSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_EurodollarMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

Credit Agreement (Details) - USD ($)	Feb. 19, 2019	Dec. 31, 2019	Feb. 21, 2019	Dec. 31, 2018
Credit agreement
Borrowing under credit agreement		$ 0		$ 0
Revolving Credit Facility
Credit agreement
Maximum borrowing capacity			$ 165,000,000
Right to increase			50,000,000
Borrower Obligations, capital stock of first-tier foreign subsidiaries, percent	65.00%
Revolving Credit Facility \| Federal Funds Effective Swap Rate
Credit agreement
Basis spread	0.50%
Revolving Credit Facility \| Eurodollar
Credit agreement
Basis spread	1.00%
Applicable margin	0.0175
Revolving Credit Facility \| Base Rate
Credit agreement
Applicable margin	0.0075
Revolving Credit Facility \| Letter of Credit Sublimit
Credit agreement
Maximum borrowing capacity			100,000,000
Revolving Credit Facility \| Revolver Swing Line Supplement
Credit agreement
Maximum borrowing capacity			$ 15,000,000