Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	5 Months Ended	7 Months Ended	12 Months Ended
	Jul. 31, 2018	Dec. 31, 2017	Jul. 31, 2018	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Income Tax [Line Items]
Corporate tax rate		35.00%	21.00%	26.90%
Unrecognized tax benefits that, if recognized, would affect the company's income tax rate	$ 10,491		$ 10,491	$ 10,491	$ 8,477	$ 8,886
Accrued interest and penalties	1,290		1,290	1,290	1,209
Total amount of interest and penalties expense (benefit) recognized				203	$ (218)	$ (231)
Expected decrease in unrecognized tax benefits due to resolution of uncertain tax positions	2,300		2,300	2,300
Expected decrease in interest due to resolution of uncertain tax positions				450
State and Local Jurisdiction
Income Tax [Line Items]
Tax credit carry forward	996		996	996
Gross state tax Net Operating Loss carry forwards	9,141		9,141	9,141
Deferred tax asset, Net Operating Loss carry forwards	525		$ 525	$ 525
State and Local Jurisdiction | Earliest Tax Year
Income Tax [Line Items]
Tax credit carry forward expiration year				2027
Gross state tax Net Operating Loss carry forwards, expiration year				2019
State and Local Jurisdiction | Latest Tax Year
Income Tax [Line Items]
Tax credit carry forward expiration year				2028
Gross state tax Net Operating Loss carry forwards, expiration year				2038
Staff Accounting Bulletin Number 118
Income Tax [Line Items]
Measurement period				1 year
Provisional tax amount of additional deferred income tax expense				$ 34,000
Provisional tax amount of additional income tax expense	$ 2,000