v3.6.0.2

Business Segments and Geographic Areas - Schedule of Accounts Receivable and Revenue by Major Customers by Reporting Segments (Detail) | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Customer Concentration Risk [Member] | Oil and Gas [Member] | Sales Revenue, Segment [Member] | Customer A [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
Concentration risk, percentage | 14.00% | 15.00% | 17.00%
Customer Concentration Risk [Member] | Oil and Gas [Member] | Sales Revenue, Segment [Member] | Customer B [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
Concentration risk, percentage | 10.00% | 11.00% | 13.00%
Customer Concentration Risk [Member] | Air Medical and Technical Services [Member] | Sales Revenue, Segment [Member] | Customer C [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
Concentration risk, percentage | 5.00% | 9.00% | 10.00%
Concentration of Credit Risk [Member] | Oil and Gas [Member] | Accounts Receivable [Member] | Customer A [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
Concentration risk, percentage | 8.00% | 6.00% |
Concentration of Credit Risk [Member] | Oil and Gas [Member] | Accounts Receivable [Member] | Customer B [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
Concentration risk, percentage | 8.00% | 9.00% |
Concentration of Credit Risk [Member] | Air Medical and Technical Services [Member] | Accounts Receivable [Member] | Customer C [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
Concentration risk, percentage | 13.00% | 15.00% |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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