Note 7 - Segment Information - Results of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2017	May 31, 2016	Aug. 31, 2016
Total assets	$ 1,358,014	$ 1,038,975	$ 1,358,014	$ 1,038,975	$ 1,019,161
Capital expenditures	7,936	8,233	25,981	34,671
Revenues from clients	312,120	287,501	894,537	839,801
Segment operating profit	87,642	89,290	269,707	261,942
UNITED STATES
Total assets	708,440	696,832	708,440	696,832
Capital expenditures	6,211	6,060	21,311	29,133
Revenues from clients	197,834	193,166	580,090	565,063
Segment operating profit	34,382	42,020	110,574	127,479
Europe [Member]
Total assets	555,366	264,910	555,366	264,910
Capital expenditures	515	913	1,176	2,181
Revenues from clients	87,327	70,243	235,464	206,198
Segment operating profit	37,766	33,304	114,282	95,536
Asia Pacific [Member]
Total assets	94,208	77,233	94,208	77,233
Capital expenditures	1,210	1,260	3,494	3,357
Revenues from clients	26,959	24,092	78,983	68,540
Segment operating profit	$ 15,494	$ 13,966	$ 44,851	$ 38,927