Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Value of equity interests (such as common shares, preferred shares, or partnership interest) issued or issuable to acquire the entity.

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Number of shares of equity interests issued or issuable to acquire entity.

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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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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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Total aggregate amount of all noninterest expense.

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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	May. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Business Acquisition [Line Items]
Noninterest Expense		$ 175,569	$ 163,851	$ 520,319	$ 485,739
WNB Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Purchase price allocation	$ 198,798
Total value of common stock issued for consideration	$ 149,700
Common stock number of shares issued for consideration	2,000,000
Amount of cash consideration	$ 49,100
Amortization period of intangible assets acquired				10 years
Acquisition-related Costs [Member]
Business Acquisition [Line Items]
Noninterest Expense			$ 1,100		$ 7,100