Reconciliation of Basic and Diluted Earnings Per Common Share (Detail) - shares shares in Thousands		12 Months Ended
		Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Earnings Per Share Disclosure [Line Items]
Weighted average basic common shares outstanding	[1]	29,225	29,156	28,151
Dilutive effect of performance based restricted stock units	[2]	42	98	45
Weighted average diluted common shares outstanding		32,562	32,468	33,328
2018 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	[3]	3,295	3,214	5,130
2026 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	[4]			2

[1] Restricted stock grants and restricted stock units, including some grants subject to certain performance criteria, are included in weighted average basic common shares outstanding when the Company is in a net earnings position. No restricted stock and restricted stock units were anti-dilutive for the years ended August 31, 2017, 2016 and 2015.

[2] Restricted stock units subject to performance criteria, for which actual levels of performance above target have been achieved, are included in weighted average diluted common shares outstanding when the Company is in a net earnings position.

[3] The dilutive effect of the 2018 Convertible notes was included as they were considered dilutive under the "if converted" method as further discussed below.

[4] The 2026 Convertible notes were retired in August 2016. The effect of the 2026 Convertible notes was excluded for the year ended August 31, 2016 as the average stock price was less than the applicable conversion price and therefore the notes were considered anti-dilutive. The dilutive effect of the 2026 Convertible notes was included for the year ended August 31, 2015 as the average stock price was greater than the applicable conversion price, as further described below.