Document and Entity Information	6 Months Ended
	Jun. 30, 2012	Aug. 01, 2012 Common Class A [Member]	Aug. 01, 2012 Common Class B [Member]
Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2
Trading Symbol	SWFT
Entity Registrant Name	SWIFT TRANSPORTATION Co
Entity Central Index Key	0001492691
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		87,039,443	52,495,236