Summary of Significant Accounting Policies and Practices - Additional Information (Detail)	3 Months Ended			6 Months Ended
	Nov. 30, 2015 USD ($) shares	Aug. 31, 2015 USD ($) shares	Nov. 30, 2014 shares	Nov. 30, 2015 USD ($) Segment Location Customer shares	Nov. 30, 2014 shares	Jul. 07, 2015 USD ($)	May. 31, 2015 USD ($)	Nov. 30, 2010
Significant Accounting Policies [Line Items]
Number of operating segments | Segment				3
Number of locations in which company operates | Location				150
Restricted cash	$ 5,000,000			$ 5,000,000
Goodwill	253,677,000			$ 253,677,000			$ 107,773,000
Number of shares estimated to be issued to acquire non-controlling interests | shares		728,266
Cash payment to acquire non controlling interest		$ 5,900,000
Deferred tax assets recovery from future taxable income percentage				50.00%
Workers compensation our self-insured retention				$ 1,000,000
Automobile liability self-insured retention				500,000
General liability claims we have an effective self-insured retention				3,000,000
Medical claims, our self-insured retention				175,000
Environmental liability claims, our self-insured retention				500,000
Amount of earned but unbilled revenue included in accounts receivable	$ 28,600,000			$ 28,600,000			$ 18,400,000
Options to purchase shares of common stock excluded from the computation of diluted earnings per share | shares	0		0	0	0
Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Number of customers accounted for more than specified percentage of consolidated revenues | Customer				0
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Percentage of consolidated revenues				10.00%
Quest Integrity [Member]
Significant Accounting Policies [Line Items]
Purchase percentage of quest								95.00%
Qualspec Group [Member]
Significant Accounting Policies [Line Items]
Restricted cash	$ 5,000,000			$ 5,000,000
Goodwill						$ 145,440,000