Fair Value Option Summary of Corporation's Mortgage Loans Held for Sale (Details) (USD $)			3 Months Ended
Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Mortgage Loans Held For Sale [Member]	Mar. 31, 2012 Mortgage Loans Held For Sale [Member]	Mar. 31, 2013 Mortgage Loans Held For Sale [Member] Cost [Member]	Dec. 31, 2012 Mortgage Loans Held For Sale [Member] Cost [Member]	Mar. 31, 2013 Mortgage Loans Held For Sale [Member] Fair Value	Dec. 31, 2012 Mortgage Loans Held For Sale [Member] Fair Value
Fair Value, Option, Quantitative Disclosures [Line Items]
Loans Held-for-sale, Mortgages	$ 63,045,000	$ 67,899,000			$ 61,590,000	$ 65,745,000	$ 63,045,000	$ 67,899,000
Gain (loss) in fair values of mortgage loans held for sale			$ (699,000)	$ (126,000)

Carrying amount of mortgage loans to individuals not classified as held for investment but are held-for-sale.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6490309&loc=d3e48678-111004

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Permanent Investor

-URI http://asc.fasb.org/extlink&oid=6520390

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6375948&loc=d3e4428-111522

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 65

-Paragraph 1, 34

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Paragraph 8

-Subparagraph h

-Chapter V

-Subsection I

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(a)(3))

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