Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Outstanding Value Of Letters Of Credit	$ 123.6	$ 129.2

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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