Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Available-for-Sale and Held-to-Maturity Investment Securities (Parenthetical) (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
State and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities transferred from available-for-sale to held-to-maturity, net unrealized gain	$ 2.6	$ 2.9

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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