Income Taxes - Additional Information (Detail)	6 Months Ended	12 Months Ended
	Jan. 31, 2018 USD ($) d	Jul. 31, 2018	Jul. 31, 2017 USD ($)
Income Taxes [Line Items]
Unrecognized tax benefits related to federal, state and foreign taxes	$ 1,800,000		$ 700,000
Expected any unrecognized tax benefits to reverse in the next twelve months	$ 0
Stockholder owning ownership on corporation's securities percentage	5.00%
Stockholder owning ownership on corporation's securities rolling period	3 years
Net operating loss carryforwards for federal tax	$ 2,100,000,000
Net operating loss carryforwards for state tax	$ 209,800,000
Business days | d	10
Statutory federal income tax rate	35.00%
Provision for income tax expense (benefit)	$ 266,300,000
Accumulated foreign earnings provisional income tax expense	$ 0
Minimum
Income Taxes [Line Items]
Percentage of ownership require to obtain approval from board of directors to acquiring shares of the company's securities	4.99%
Parent Company
Income Taxes [Line Items]
Provision for income tax expense (benefit)	$ 296,100,000
IWCO
Income Taxes [Line Items]
Deferred tax liability	79,900,000
Provision for income tax expense (benefit)	$ (29,800,000)
Scenario, Forecast
Income Taxes [Line Items]
Statutory federal income tax rate		21.00%
Federal | Internal Revenue Service (IRS) | Earliest Tax Year
Income Taxes [Line Items]
Tax examinations tax period	2013
Federal | Internal Revenue Service (IRS) | Latest Tax Year
Income Taxes [Line Items]
Tax examinations tax period	2017
State | Earliest Tax Year
Income Taxes [Line Items]
Tax examinations tax period	2013
State | Latest Tax Year
Income Taxes [Line Items]
Tax examinations tax period	2017
Foreign | Europe Income Tax Authority | Earliest Tax Year
Income Taxes [Line Items]
Tax examinations tax period	2009
Foreign | Europe Income Tax Authority | Latest Tax Year
Income Taxes [Line Items]
Tax examinations tax period	2016
Foreign | Asia Income Tax Authority | Earliest Tax Year
Income Taxes [Line Items]
Tax examinations tax period	2005
Foreign | Asia Income Tax Authority | Latest Tax Year
Income Taxes [Line Items]
Tax examinations tax period	2016