Note 17 - Commitments and Contingencies (Details Textual) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2018 USD ($) ft² a	Feb. 28, 2017 USD ($)	Feb. 28, 2018 USD ($) ft² a	Feb. 28, 2017 USD ($)	Feb. 14, 2018 ft²	Nov. 30, 2017 USD ($)	Aug. 31, 2017 USD ($)
Operating Leases, Rent Expense	$ 13,500	$ 11,500	$ 26,500	$ 22,900
Other Liabilities, Noncurrent	37,738		37,738				$ 37,188
Letters of Credit Outstanding, Amount	$ 1,900		$ 1,900
Purchase Commitment, Remaining Minimum Amount Committed						$ 81,000
Largest Individual Client Percent Of Total Subscriptions	2.00%		2.00%
Percentage of Subscription from Ten Largest Clients	15.00%		15.00%
Allowance for Doubtful Accounts Receivable	$ 3,300		$ 3,300				2,700
Deferred Rent [Member]
Other Liabilities	38,400		38,400				37,400
Other Liabilities, Noncurrent	$ 34,100		$ 34,100				$ 33,500
Norwalk Connecticut [Member]
Area of Real Estate Property | ft²	202,000		202,000		173,000
Non-cancelable Operating Lease [Member]
Area of Real Estate Property | a	1,760,000		1,760,000
Increase (Decrease) in Area of Real Estate Property | a	617,000		617,000
Increase (Decrease) in Area of Real Estate Property, Percent			54.00%