Refranchising (Narrative) (Details) $ in Thousands	3 Months Ended			9 Months Ended
	May 31, 2018 USD ($) franchise	May 31, 2017 USD ($) franchise	Nov. 30, 2016 franchise	May 31, 2018 franchise	May 31, 2017 USD ($) franchise
Franchisor Disclosure [Line Items]
Refranchised company drive-ins	2	5		8	5
Franchise restaurant ownership target	95.00%			95.00%
2017 Refranchising [Member]
Franchisor Disclosure [Line Items]
Refranchising initiative gains, net | $		$ 814			$ 6,645
Refranchised company drive-ins		0	53		110
2018 Refranchising [Member]
Franchisor Disclosure [Line Items]
Refranchising initiative gains, net | $	$ 3,200
Refranchised company drive-ins	41