Quarterly report pursuant to Section 13 or 15(d)

Property and Equipment, Net of Accumulated Depreciation (Narrative) (Details)

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Property and Equipment, Net of Accumulated Depreciation (Narrative) (Details)
$ in Millions
 1 Months Ended 3 Months Ended
Oct. 05, 2017
USD ($)
item
Sep. 30, 2017
Aug. 31, 2017
USD ($)
ft²
item
Aug. 31, 2017
USD ($)
ft²
item
Aug. 31, 2016
USD ($)
Property, Plant and Equipment [Line Items]          
Depreciation expense       $ 28.1 $ 25.3
Cost of building purchased       $ 18.0 $ 20.3
Multi-Building Campus [Member] | Subsequent Event [Member] | County Of Monroe Industrial Development Agency [Member]          
Property, Plant and Equipment [Line Items]          
Public benefits and inducements expiration date   Dec. 31, 2039      
Multi-Building Campus [Member] | Rochester, NY [Member]          
Property, Plant and Equipment [Line Items]          
Number of buildings planned to be purchased | item     5 5  
Renovation square feet | ft²     300,000 300,000  
Estimated cost of building to be purchased     $ 60.0    
Multi-Building Campus [Member] | Rochester, NY [Member] | Subsequent Event [Member]          
Property, Plant and Equipment [Line Items]          
Number of buildings purchased | item 2        
Cost of building purchased $ 19.5