Equity - Additional Information (Detail) - USD ($)			12 Months Ended			48 Months Ended
	Oct. 27, 2017	Sep. 30, 2017	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015	Aug. 31, 2017	Jan. 31, 2013
Stockholders Equity Note [Line Items]
Maximum aggregate number of common shares authorized for issuance							4,325,000
Shares available for grant			233,271	476,770	905,139	233,271
Performance based share based compensation			269,705	447,895	402,196
Share based compensation, non vested shares			492,886			492,886
Additional shares available for grant			492,886
Unamortized compensation cost of restricted stock grants			$ 14,100,000			$ 14,100,000
Selling, Administrative and Cost of Revenue
Stockholders Equity Note [Line Items]
Restricted stock compensation expense			$ 20,200,000	$ 22,500,000	$ 19,500,000
Share Repurchase Program - 2014
Stockholders Equity Note [Line Items]
Repurchase of common stock, shares			0	1,054,687		3,206,226
Stock repurchase program total cost of repurchased shares				$ 32,400,000		$ 137,000,000
Remaining authorized repurchase amount			$ 88,000,000			88,000,000
Repurchase program expiration date			Jan. 01, 2018
Subsequent Event | Share Repurchase Program - 2014
Stockholders Equity Note [Line Items]
Repurchase program expiration date	Mar. 31, 2019	Jan. 01, 2018
Maximum | Share Repurchase Program - 2013
Stockholders Equity Note [Line Items]
Amount authorized for repurchase			$ 225,000,000			$ 225,000,000
Unvested Restricted Stock Grants
Stockholders Equity Note [Line Items]
Share based compensation, non vested shares			837,654	902,068		837,654
Fair value of awards granted			$ 11,300,000	$ 12,500,000	$ 24,600,000
Restricted Stock | Minimum
Stockholders Equity Note [Line Items]
Vesting period of compensation expense			1 year
Restricted Stock | Maximum
Stockholders Equity Note [Line Items]
Vesting period of compensation expense			3 years