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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Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

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Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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The amount of identifiable intangible assets recognized as of the acquisition date.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Business Combinations - Additional Information (Detail)			1 Months Ended	6 Months Ended
Business Combinations - Additional Information (Detail)	Oct. 09, 2015 USD ($) $ / shares shares	Mar. 02, 2015 USD ($) shares	Aug. 31, 2016 USD ($)	Jun. 30, 2016 USD ($) Branch	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Assets				$ 5,834,107,000	$ 5,584,637,000
Loans				3,801,240,000	3,729,050,000
Deposits				3,992,139,000	4,016,566,000
Goodwill resulting from acquisition of FNBW				$ 84,852,000	85,212,000
Penn Liberty Financial Corporation [Member] \| Pennsylvania [Member]
Business Acquisition [Line Items]
Assets					704,000,000
Loans					510,000,000
Deposits					621,000,000
Number of branch locations \| Branch				11
Agreement date of merger				Nov. 23, 2015
Alliance Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Goodwill resulting from acquisition of FNBW				$ 36,065,000	$ 36,425,000
Alliance Bancorp, Inc. [Member] \| Pennsylvania [Member]
Business Acquisition [Line Items]
Transaction value, cash and stock	$ 97,921,000
Agreement date of merger				Mar. 02, 2015
Cash paid to Alliance stockholders	$ 26,576,000	$ 26,600,000
Common stock shares issued \| shares	2,459,120	2,459,120
Effective date of merger				Oct. 09, 2015
Goodwill resulting from acquisition of FNBW	$ 36,065,000
Alliance Bancorp, Inc. [Member] \| Pennsylvania [Member] \| NASDAQ Global Select Market [Member]
Business Acquisition [Line Items]
Closing share price \| $ / shares	$ 29.01
Alliance Bancorp, Inc. [Member] \| Pennsylvania [Member] \| Core Deposits [Member]
Business Acquisition [Line Items]
Intangibles	$ 2,600,000
Amortized period	10 years
Alliance Bancorp, Inc. [Member] \| Pennsylvania [Member] \| Non-compete Covenants [Member]
Business Acquisition [Line Items]
Intangibles	$ 511,000
Alliance Bancorp, Inc. [Member] \| Pennsylvania [Member] \| Non-compete Covenants [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Amortized period	6 months
Alliance Bancorp, Inc. [Member] \| Pennsylvania [Member] \| Non-compete Covenants [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Amortized period	18 months
Scenario, Forecast [Member] \| Penn Liberty Financial Corporation [Member] \| Pennsylvania [Member]
Business Acquisition [Line Items]
Transaction value, cash and stock			$ 101,000,000