Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2019	Mar. 31, 2019	Mar. 31, 2018
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill, net, beginning of period		$ 2,022	$ 0
Additions		1,157	2,022
Goodwill, net, end of period	$ 3,179	3,179	2,022
Defense and Intelligence
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill, net, beginning of period		977	0
Additions	1,100	1,074	977
Goodwill, net, end of period	2,051	2,051	977
Civilian and Health Care
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill, net, beginning of period		1,045	0
Additions	77	83	1,045
Goodwill, net, end of period	$ 1,128	$ 1,128	$ 1,045

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

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- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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