Maximum potential amount of future undiscounted payments that could be required under the credit derivative, before reduction for potential recoveries under recourse or collateralization provisions.

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Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

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Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

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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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Derivative Financial Instruments (Counterparty Credit Risk Narrative) (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative instrument asset, Amount Offset		$ 8,100	$ 4,936
Derivative, Collateral, Right to Reclaim Cash	$ 121,600
Credit Derivative, Maximum Exposure, Undiscounted	132,300
Valuation, Cost Approach [Member]
Derivative [Line Items]
Derivative, Collateral, Right to Reclaim Cash	8,400
Valuation, Market Approach [Member]
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	39,600
CME SWAPS MARKETS (CME) [Member]
Derivative [Line Items]
Derivative instrument asset, Amount Offset	56,600
Derivative, Collateral, Right to Reclaim Cash	$ 71,300