Concentration of Risk and Segment Data (Segment Assets) (Details) - USD ($) $ in Thousands	Aug. 31, 2018	Aug. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 12,045,641	$ 11,095,995
EMS
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,456,866	2,778,820
DMS
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	5,378,436	5,290,468
Other non-allocated assets
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 3,210,339	$ 3,026,707