CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Treasury Stock	Noncontrolling Interests
Beginning Balance at Aug. 31, 2015	$ 2,335,011	$ 247	$ 1,955,104	$ 1,468,910	$ (50,854)	$ (1,058,551)	$ 20,155
Beginning Balance (in shares) at Aug. 31, 2015		192,068,068
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercise of stock options (in shares)		19,109
Shares issued under employee stock purchase plan	20,911	$ 1	20,910
Shares issued under employee stock purchase plan (in shares)		1,246,947
Vesting of restricted stock awards	0	$ 2	(2)
Vesting of restricted stock awards (in shares)		1,817,635
Purchases of treasury stock under employee stock plans	(10,656)					(10,656)
Purchases of treasury stock under employee stock plans (in shares)		(462,900)
Treasury shares purchased	(148,340)					(148,340)
Treasury shares purchased (in shares)		(7,690,387)
Recognition of stock-based compensation	58,997		58,997
Declared dividends	(62,185)			(62,185)
Comprehensive income	265,873			254,095	10,977		801
Declared dividends to noncontrolling interests	(1,500)						(1,500)
Purchase of noncontrolling interests	(600)		(484)				(116)
Foreign currency adjustments attributable to noncontrolling interests	(14)						(14)
Ending Balance at Aug. 31, 2016	2,457,497	$ 250	2,034,525	1,660,820	(39,877)	(1,217,547)	19,326
Ending Balance (in shares) at Aug. 31, 2016		186,998,472
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercise of stock options (in shares)		172,620
Shares issued under employee stock purchase plan	21,792	$ 1	21,791
Shares issued under employee stock purchase plan (in shares)		1,228,316
Vesting of restricted stock awards	0	$ 2	(2)
Vesting of restricted stock awards (in shares)		2,102,049
Purchases of treasury stock under employee stock plans	(12,268)					(12,268)
Purchases of treasury stock under employee stock plans (in shares)		(550,096)
Treasury shares purchased	(306,640)					(306,640)
Treasury shares purchased (in shares)		(12,223,708)
Recognition of stock-based compensation	47,889		47,889
Declared dividends	(59,017)			(59,017)
Comprehensive income	221,664			129,090	94,497		(1,923)
Declared dividends to noncontrolling interests	(2,293)						(2,293)
Purchase of noncontrolling interests	(134)						(134)
Foreign currency adjustments attributable to noncontrolling interests	(146)						(146)
Ending Balance at Aug. 31, 2017	$ 2,368,344	$ 253	2,104,203	1,730,893	54,620	(1,536,455)	14,830
Ending Balance (in shares) at Aug. 31, 2017	177,727,653	177,727,653
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercise of stock options (in shares)		30,832
Shares issued under employee stock purchase plan	$ 24,866	$ 1	24,865
Shares issued under employee stock purchase plan (in shares)		1,105,400
Vesting of restricted stock awards		$ 3	(3)
Vesting of restricted stock awards (in shares)		2,727,229
Purchases of treasury stock under employee stock plans	(22,597)					(22,597)
Purchases of treasury stock under employee stock plans (in shares)		(793,052)
Treasury shares purchased	(450,319)					(450,319)
Treasury shares purchased (in shares)		(16,209,890)
Recognition of stock-based compensation	89,608		89,608
Declared dividends	(57,126)			(57,126)
Comprehensive income	13,522			86,330	(74,019)		1,211
Declared dividends to noncontrolling interests	(2,920)						(2,920)
Foreign currency adjustments attributable to noncontrolling interests	2						2
Ending Balance at Aug. 31, 2018	$ 1,963,380	$ 257	$ 2,218,673	$ 1,760,097	$ (19,399)	$ (2,009,371)	$ 13,123
Ending Balance (in shares) at Aug. 31, 2018	164,588,172	164,588,172