Income Taxes - Reconciliation of effective tax rate (Details)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
Federal income tax, at statutory rate	34.00%	34.00%	34.00%
State taxes, net of Federal tax benefit	2.80%	3.60%	(3.70%)
Tax exempt investment security income, net	(16.70%)	(14.00%)	(34.70%)
Bank owned life insurance, net	(1.40%)	(1.60%)	(4.60%)
Solar credits	(1.40%)	(1.60%)	(5.40%)
Change in uncertain tax positions	0.50%	0.50%	(1.30%)
Other	0.50%	1.40%	3.00%
Effective tax rate	18.30%	22.30%	(12.70%)

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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-Publisher SEC

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-Number 210

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 47

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to nondeductible life insurance premiums under enacted tax laws.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to all other items not otherwise listed in the existing taxonomy.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate that can be explained by the state and local income tax expense or benefit, net of the federal tax benefit (expense) thereon, recorded during the period.

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The sum of the differences between the effective income tax rate and domestic federal statutory income tax rate attributable to changes in all income tax contingencies, whether recorded or adjusted, during the period.

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The sum of the differences between the effective income tax rate and domestic federal statutory income tax rate that can be explained by all tax credits generated or utilized under enacted tax laws during the period.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to income that is exempt from income taxes under enacted tax laws.

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