Accrued Interest Receivable (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Accrued Interest Receivable
Investment securities	$ 2,205	$ 2,354
Mortgage-backed securities	1,079	1,359
Loans receivable	18,537	19,600
Accrued interest receivable	$ 21,821	$ 23,313

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Amounts due for interest earned on investment securities but not received as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	nwbi_AccruedInterestReceivableOnInvestments
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- Definition

Amounts due for interest earned on loans but not received as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	nwbi_AccruedInterestReceivableOnLoans
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- Definition

Amounts due for interest earned on mortgage-backed securities but not received as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	nwbi_AccruedInterestReceivableOnMortgageBackedSecurities
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- Definition

Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

+ 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 210.5-02.8)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 8

-Article 5

+ Details

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