Note Fair Value of financial instruments- Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Letter Of Credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure Off balance Sheet Risks Face Amount Asset	$ 32	$ 36
Commitments To Extend Credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure Off balance Sheet Risks Face Amount Asset	$ 7,200	$ 7,600

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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