Acquisitions - HPES Merger Additional Information (Details) $ / shares in Units, $ in Millions			3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 25, 2017 USD ($)	Apr. 01, 2017 USD ($) shares	Dec. 31, 2017 USD ($)	Dec. 18, 2017 USD ($)	Sep. 30, 2017 USD ($)	Dec. 30, 2016 USD ($) $ / shares	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 30, 2016 USD ($) $ / shares	Mar. 31, 2017 USD ($) tranche		May 31, 2016 USD ($)
Business Acquisition [Line Items]
Goodwill			$ 9,320					$ 9,320		$ 1,855	[1]
Adjustment to net income for nonrecurring transaction costs			779			$ 37		1,217	$ 38
HPES
Business Acquisition [Line Items]
Shares issued for each share of CSC common stock (in shares) | shares		1
Shares issued for merger consideration (in shares) | shares		141,298,797
Percent ownership of CSC stockholders following the Merger		49.90%
Adjustment to settle obligations	$ 203			$ 203
Adjustment to capital lease obligations					$ 977			1,000
Adjustment to property, plant, and equipment								317
Adjustment to net assets								450
Adjustment to assets								1,200
Adjustment to accounts receivable								127
Adjustment to intangible assets								1,100
Adjustment to liabilities								1,700
Adjustment to deferred revenue								343
Adjustment to long-term debt								106
Adjustment to debt			12					94
Adjustment to long-term income tax liabilities								200
Goodwill		$ 7,208
Acquired restructuring liabilities		328
Long-term debt		4,817
Adjustment to deferred debt issuance costs, premiums and discounts								12
Capital lease obligation			1,600					1,600
Net income (loss)						$ (166)			$ (570)
Loss per common share, Basic (in dollars per share) | $ / shares						$ (0.61)			$ (2.07)
Loss per common share, Diluted (in dollars per share) | $ / shares						$ (0.61)			$ (2.07)
HPES | Employee severance
Business Acquisition [Line Items]
Acquired restructuring liabilities		256
HPES | Facilities costs
Business Acquisition [Line Items]
Acquired restructuring liabilities		$ 72
HPES | Senior notes
Business Acquisition [Line Items]
Long-term debt										1,800
HPES | Term Loan
Business Acquisition [Line Items]
Long-term debt										$ 2,000
Number of tranches | tranche										3
Hewlett Packard Enterprise Company
Business Acquisition [Line Items]
Debt and accrued interest			87					87
Customer relationships | HPES
Business Acquisition [Line Items]
Adjustment to intangible assets								1,300
Assets Held under Capital Leases | HPES
Business Acquisition [Line Items]
Adjustment to property, plant, and equipment					594			594
Adjustment to goodwill					$ 383
Land and Data Centers | HPES
Business Acquisition [Line Items]
Adjustment to property, plant, and equipment								(277)
Accounting Standards Update 2015-16 | HPES
Business Acquisition [Line Items]
Adjustment to income (loss) before income taxes							$ 16
Adjustment to interest expense related to capital lease			9
Adjustment to cost of services			7
Maximum | HPES | HPES
Business Acquisition [Line Items]
Lease obligation												$ 250
GBS
Business Acquisition [Line Items]
Goodwill			4,364					4,364		$ 1,470
GBS | HPES
Business Acquisition [Line Items]
Goodwill			2,700					2,700
GIS
Business Acquisition [Line Items]
Goodwill			2,972					2,972		385
GIS | HPES
Business Acquisition [Line Items]
Goodwill			2,500					2,500
USPS
Business Acquisition [Line Items]
Goodwill			1,984					1,984		0
USPS | HPES
Business Acquisition [Line Items]
Goodwill			$ 2,000					2,000
Senior Notes, Issued 2017 | HPES | Senior notes
Business Acquisition [Line Items]
Long-term debt										1,500
Senior Notes, Issued 1999 | HPES | Senior notes
Business Acquisition [Line Items]
Long-term debt										$ 300
Acquisition-related Costs | HPES
Business Acquisition [Line Items]
Adjustment to net income for nonrecurring transaction costs								$ (26)
Net income (loss)						$ (96)			$ (292)
Loss per common share, Basic (in dollars per share) | $ / shares						$ (0.34)			$ (1.03)
Loss per common share, Diluted (in dollars per share) | $ / shares						$ (0.34)			$ (1.03)

[1] Certain prior year amounts were adjusted to retroactively reflect the legal capital of DXC.