Contractual interest rate for funds borrowed, under the debt agreement.

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Debt - Partial Redemption of 4.125% Senior Secured Notes - Additional Information (Detail) € in Thousands, $ in Millions			3 Months Ended		6 Months Ended
	Oct. 12, 2018 USD ($)	Oct. 12, 2018 EUR (€)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Apr. 30, 2019	Oct. 09, 2018
Debt Instrument [Line Items]
Loss on extinguishment of debt \| $			$ 0	$ 0	$ 0	$ 3
4.125% Senior Secured Notes due 2024
Debt Instrument [Line Items]
Interest rate			4.125%	4.125%	4.125%	4.125%
4.125% Senior Secured Notes due 2024 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate		4.125%	4.125%		4.125%			4.125%
Redemptions of senior notes		€ 34,500
Due date of senior secured notes	2024	2024			2024
Senior notes redemption price		€ 36,170
Redemption price, percentage of principal amount redeemed	103.00%	103.00%
Debt instrument remaining outstanding amount		€ 310,500
Loss on extinguishment of debt \| $	$ 2
3.625% Senior Secured Notes due 2026
Debt Instrument [Line Items]
Interest rate			3.625%	3.625%	3.625%	3.625%
3.625% Senior Secured Notes due 2026 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate			3.625%		3.625%		3.625%	3.625%
Due date of senior secured notes					2026