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Name:	us-gaap_ObligationWithJointAndSeveralLiabilityArrangementLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Commitments and Contingencies - Additional Information (Detail) - USD ($)	Sep. 30, 2019	Apr. 02, 2019	Apr. 01, 2019
Obligation with Joint and Several Liability Arrangement [Line Items]
Letters of credit facility outstanding		$ 150,000,000	$ 155,000,000
Letter of Credit
Obligation with Joint and Several Liability Arrangement [Line Items]
Letter of credit maximum available amount	$ 250,000,000