Provision for Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		5 Months Ended	6 Months Ended		7 Months Ended	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Dec. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Jul. 31, 2018	Jul. 31, 2018
Income Tax [Line Items]
Effective income tax rate	43.50%	34.10%		36.60%	33.00%
Corporate tax rate			35.00%
Reduction of net deferred tax assets due to change in tax rate				$ 34,000
Tax expense (benefit) recorded from applying lower federal income tax rate	$ 12,535
Additional income tax expense benefit due to change in tax rate				34,000
Expected decrease in unrecognized tax benefits due to resolution of uncertain tax positions	$ 2,730			2,730
Expected decrease in interest due to resolution of uncertain tax positions				$ 370
Scenario Forecast
Income Tax [Line Items]
Corporate tax rate						21.00%	26.90%