Reconciliation of Basic and Diluted Earnings Per Common Share (Detail) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Feb. 28, 2015		Feb. 28, 2014		Feb. 28, 2015		Feb. 28, 2014
Earnings Per Share Disclosure [Line Items]
Weighted average basic common shares outstanding	27,028	[1]	28,300	[1]	27,348	[1]	28,359	[1]
Weighted average diluted common shares outstanding	33,073		34,345		33,395		34,404
2018 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	6,044	[2]	6,045	[2]	6,044	[2]	6,045	[2]
2026 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	1	[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 six months ended February 28, 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 six months ended February 28, 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 six months ended February 28, 2014 as the average stock price was less than $48.05 and therefore was considered anti-dilutive.