Legal proceedings and contingencies (Details) - Exelis - Passaic River Alaska $ in Millions		3 Months Ended
Mar. 31, 2016 party	Sep. 30, 2016 USD ($)
Loss Contingencies [Line Items]
Estimated cost for all participating parties of EPA's preferred alternative \| $		$ 1,380
Number of responsible parties notified \| party	100

Best estimate of the loss exposure for reasonably possible environmental contingencies at an individual site for which no accrual has been recorded.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (c),(d)(2)
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

Name:	us-gaap_SiteContingencyLossExposureNotAccruedBestEstimate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration