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Summary of significant accounting policies (Narrative) (Details) shares in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 USD ($) reporting_unit | Dec. 31, 2015 USD ($) reporting_unit | Dec. 31, 2014 USD ($) shares
Property, Plant and Equipment [Line Items] |  |  |
Impairment of long-lived assets | $ 4,300,000 | $ 0 | $ 0
Goodwill and Intangible Asset Impairment [Abstract] |  |  |
Number of reporting units | reporting_unit | 6 | 6 |
Impairment | $ 0 | $ 123,200,000 | 0
Estimated useful life, intangible assets | 14 years |  |
Impairment of intangible assets | $ 0 |  | $ 0
Earnings (loss) per share |  |  |
Diluted earnings per share calculation excluded shares (in shares) | shares |  |  | 0.5
Subsea Technologies |  |  |
Goodwill and Intangible Asset Impairment [Abstract] |  |  |
Impairment |  | 123,200,000 |
Subsea Technologies | Trade names |  |  |
Goodwill and Intangible Asset Impairment [Abstract] |  |  |
Impairment of intangible assets |  | $ 1,900,000 |
Minimum |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated useful life, property and equipment | 3 years |  |
Goodwill and Intangible Asset Impairment [Abstract] |  |  |
Estimated useful life, intangible assets | 3 years |  |
Minimum | Trade names |  |  |
Goodwill and Intangible Asset Impairment [Abstract] |  |  |
Estimated useful life, intangible assets | 10 years | 10 years |
Minimum | Rental Equipment |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated useful life, property and equipment | 3 years |  |
Maximum |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated useful life, property and equipment | 30 years |  |
Goodwill and Intangible Asset Impairment [Abstract] |  |  |
Estimated useful life, intangible assets | 17 years |  |
Maximum | Trade names |  |  |
Goodwill and Intangible Asset Impairment [Abstract] |  |  |
Estimated useful life, intangible assets | 15 years | 15 years |
Maximum | Rental Equipment |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated useful life, property and equipment | 10 years |  |

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- Definition Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13777-109266 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
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