Summary of Significant Accounting Policies - Goodwill and Other Intangible Assets (Details) $ in Millions	12 Months Ended
	Sep. 30, 2019 USD ($)
Measurement Input, Discount Rate | Goodwill and Indefinite-lived Intangible Assets | Income Approach Valuation Technique | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rates used for reporting unit valuations	0.10
Measurement Input, Discount Rate | Goodwill and Indefinite-lived Intangible Assets | Income Approach Valuation Technique | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rates used for reporting unit valuations	0.15
Guatemala, El Salvador, Honduras and Peru
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Potential goodwill impairment loss	$ 34.5
Percentage of fair value in excess of carrying value	7.00%