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Schedule of Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands | 4 Months Ended | 5 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jul. 31, 2017 | Dec. 31, 2017 | Dec. 31, 2018 | Mar. 31, 2017
Schedule Of Unrecognized Tax Benefits [Line Items] |  |  |  |
Begining Balance |  | $ 402,868 | $ 404,571 |
Additions based on tax positions related to the current year |  | 170 |  |
Additions based on tax positions related to a prior year |  | 2,578 | 6,903 |
Settlement and lapse of statute of limitations |  | (1,045) | (2,953) |
Reductions based on tax positions related to a prior year |  |  | (18,086) |
Ending Balance | $ 402,868 | 404,571 | 399,292 |
Predecessor |  |  |  |
Schedule Of Unrecognized Tax Benefits [Line Items] |  |  |  |
Begining Balance | 400,818 | $ 402,868 |  | $ 401,375
Additions based on tax positions related to the current year | 2,050 |  |  | 551
Settlement and lapse of statute of limitations |  |  |  | (1,108)
Ending Balance | $ 402,868 |  |  | $ 400,818
GulfMark |  |  |  |
Schedule Of Unrecognized Tax Benefits [Line Items] |  |  |  |
Additions from GulfMark business combination |  |  | $ 8,857 |

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- Definition Amount of unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 10B -URI http://asc.fasb.org/extlink&oid=84176650&loc=SL37586934-109318 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
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- Definition Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
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- Definition Amount of increase in unrecognized tax benefits resulting from acquisitions. + References No definition available. + Details
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- Definition Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
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