Unapproved change orders and claims (Schedule) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Contractors [Abstract]
Unapproved change orders	$ 31	$ 115
Changes in estimates at completion	71	87
Adjustments due to approvals	(42)	(171)
Adjustment due to dispositions of businesses	(14)	0
Unapproved change orders	46	31
Unapproved Change Orders And Claims Recorded In Revenues	$ 41	$ 24

The amount of costs incurred on unapproved change orders when it is probable that the cost will be recovered through a change in the contract price.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 910
-SubTopic 310
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51673017&loc=d3e49324-109356

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 910
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=51666792&loc=d3e50000-109363

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 3
-Subparagraph c(3)
-Article 5

Name:	us-gaap_UnapprovedChangeOrdersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant