Derivative Instruments and Hedging Activities - Summary of Offsetting of Financial Assets and Derivative Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Offsetting Assets [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet	$ 22,613	$ 9,752
Interest Rate Swaps
Offsetting Assets [Line Items]
Gross Amount of Recognized Assets	20,688	5,930
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	20,688	5,930
Gross amounts not offset in the consolidated balance sheet, Financial instruments	0	0
Gross amounts not offset in the consolidated balance sheet, Cash collateral received	19,330	5,070
Gross amounts not offset in the consolidated balance sheet, Net amount	$ 1,358	$ 860

Derivative Asset Fair Value of Derivative Liability not Offset

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Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, after effects of master netting arrangements, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset offset against an obligation to return collateral. Includes assets not subject to a master netting arrangement and not elected to be offset.

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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.

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