Summary of Significant Accounting Policies (Details)	9 Months Ended
Sep. 30, 2015
Minimum
Marketable securities, maturity	1 year
Maximum
Marketable securities, maturity	3 years

Represents the maturity period of long term marketable securities. Minimum Member

No definition available.

Name:	w_MarketableSecuritiesMaturityPeriod
Namespace Prefix:	w_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration