Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228

Reference 2: 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=98514028&loc=d3e3602-108585

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

Seismic Data Library (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Seismic Data Library (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jul. 01, 2018
Subsequent Event [Line Items]
Straight-line amortization period			4 years
Internal data processing costs capitalized	$ 0.6	$ 0.6	$ 1.2	$ 1.3
Lowest amortization rate using the income forecast method			70.00%
Asset impairment charges			$ 0.0	$ 0.0
Subsequent Event
Subsequent Event [Line Items]
Actual aggregate rate of amortization					70.00%