Summary of Significant Accounting Policies - PP&E (Details)	12 Months Ended
	Sep. 30, 2016
Computers and purchased software | Minimum
Property and Equipment
Estimated useful life	1 year
Computers and purchased software | Maximum
Property and Equipment
Estimated useful life	5 years
Office equipment | Minimum
Property and Equipment
Estimated useful life	3 years
Office equipment | Maximum
Property and Equipment
Estimated useful life	5 years
Furniture and fixtures | Minimum
Property and Equipment
Estimated useful life	5 years
Furniture and fixtures | Maximum
Property and Equipment
Estimated useful life	7 years
Buildings
Property and Equipment
Estimated useful life	39 years