Reconciliation of Basic and Diluted Earnings Per Common Share (Detail) - shares shares in Thousands		3 Months Ended		9 Months Ended
		May 31, 2016	May 31, 2015	May 31, 2016	May 31, 2015
Earnings Per Share Disclosure [Line Items]
Weighted average basic common shares outstanding	[1]	29,059	27,842	29,182	27,514
Dilutive effect of performance based restricted stock units	[2]	59		91
Weighted average diluted common shares outstanding		32,342	33,000	32,475	33,262
2018 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	[3]	3,224	5,155	3,202	5,745
2026 Senior Notes
Earnings Per Share Disclosure [Line Items]
Dilutive effect of convertible notes	[4]		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] Restricted stock units that are 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 for the three and nine months ended May 31, 2016 and 2015 as they were considered dilutive under the "if converted" method as further discussed below.

[4] The dilutive effect of the 2026 Convertible notes was excluded for the three and nine months ended May 31, 2016 as the average stock price was less than the conversion price of $47.15 and therefore was considered anti-dilutive. The 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 the applicable conversion price, as further described below.