Acquisitions - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Aug. 27, 2012
Business Acquisition [Line Items]
Purchase consideration per common share			$ 0.08403
Percentage of total equity consideration			60.00%
Percentage of total cash consideration			40.00%
Total consideration to be paid	$ 5,300,000
Assets	97,797,062	$ 96,685,535
Loans	67,606,450	65,749,394
Investment securities	14,494,539	12,993,542
Liabilities	84,875,128	84,349,639
Deposits	72,944,543	$ 73,582,053
Hudson City [Member]
Business Acquisition [Line Items]
Assets	35,100,000
Loans	19,200,000
Investment securities	8,300,000
Liabilities	30,300,000
Deposits	$ 17,900,000

Total consideration to be paid for the acquisition as valued as of the end of the reporting period.

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- Definition

Purchase consideration cash percentage.

+ References

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- Definition

Purchase consideration equity percentage.

+ References

No definition available.

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- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.18)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Article 7

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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.

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

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Sum of the carrying amounts as of the balance sheet date of all investments.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

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-Paragraph 1

-Subparagraph (SX 210.7-03.1(h))

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Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.

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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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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7)

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