Securities (Securities - Additional Information) (Detail) - USD ($) $ in Billions	Mar. 31, 2019	Dec. 31, 2018
Investment Holdings
Securities with a fair value, pledged as collateral	$ 7.1	$ 7.0

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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