Reconciliation of Basic and Diluted Earnings Per Common Share (Detail) - shares shares in Thousands		3 Months Ended		9 Months Ended
		May. 31, 2015	May. 31, 2014	May. 31, 2015	May. 31, 2014
Earnings Per Share Disclosure [Line Items]
Weighted average basic common shares outstanding	[1]	27,842	27,956	27,514	28,223
Weighted average diluted common shares outstanding		33,000	34,001	33,262	34,268
2018 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	[2]	5,155	6,045	5,745	6,045
2026 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	[3]	3		3

[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] The dilutive effect of the 2018 Convertible notes was included for the three and nine months ended May 31, 2015 and 2014 as they were considered dilutive under the "if converted" method as further discussed below.

[3] The dilutive effect of the 2026 Convertible notes was included for the three and nine months ended May 31, 2015 as the average stock price was greater than $48.05, as further described below. The effect of the 2026 Convertible notes was excluded for the three and nine months ended May 31, 2014 as the average stock price was less than $48.05 and therefore was considered anti-dilutive.