Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	2 Months Ended	3 Months Ended	12 Months Ended
Dec. 31, 2017	Jan. 31, 2019	Jan. 31, 2018	Oct. 31, 2018
Income Tax [Line Items]
Effective tax rates		28.60%	(1.00%)
U.S. federal corporate income tax rate	35.00%	21.00%		23.30%
Provisional discrete tax (benefit) expense		$ 4,866	$ (22,089)
Discrete tax benefit		$ 868	$ 4,748
Maximum [Member]
Income Tax [Line Items]
Measurement period		1 year

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration