Reconciliation of Basic and Diluted Earnings Per Common Share (Detail) - shares shares in Thousands		3 Months Ended		6 Months Ended
		Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2017	Feb. 29, 2016
Earnings Per Share Disclosure [Line Items]
Weighted average basic common shares outstanding	[1]	29,130	29,098	29,113	29,244
Dilutive effect of performance based restricted stock units	[2]	10	59	34	108
Weighted average diluted common shares outstanding		32,427	32,360	32,423	32,542
2018 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	[3]	3,287	3,203	3,276	3,190
2024 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	[4]	0	0	0	0
2026 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	[5]	0	0	0	0

[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.

[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 2024 Convertible notes were issued in February 2017. The dilutive effect of the 2024 Convertible notes was excluded for the three and six months ended February 28, 2017 as the average stock price was less than the applicable conversion price and therefore was considered anti-dilutive.

[5] The 2026 Convertible notes were retired in August 2016. The dilutive effect of the 2026 Convertible notes was excluded for the three and six months ended February 29, 2016 as the average stock price was less than the applicable conversion price and therefore was considered anti-dilutive.