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Acquisitions - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
Jan. 02, 2015
Jun. 27, 2014
Oct. 17, 2013
Sep. 12, 2013
Business Acquisition [Line Items]        
Value allocated to goodwill $ 2,566us-gaap_Goodwill $ 2,559us-gaap_Goodwill    
Virident [Member]        
Business Acquisition [Line Items]        
Value allocated to goodwill     506us-gaap_Goodwill
/ us-gaap_BusinessAcquisitionAxis
= wdc_ViridentMember
 
sTec [Member]        
Business Acquisition [Line Items]        
Value allocated to goodwill       $ 89us-gaap_Goodwill
/ us-gaap_BusinessAcquisitionAxis
= wdc_STecMember