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12/31/2010
USD ($)
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12/31/2009
USD ($)
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12/31/2008
USD ($)
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12/31/2010
USD ($)
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12/31/2009
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
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 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
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 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
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 -Paragraph 1
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 13

Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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 -Paragraph 1
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12/31/2009
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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 -Name Regulation S-X (SX)
 -Number 210
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 -Paragraph 1
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 -Article 7

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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
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 -Paragraph 1
 -Subparagraph a, f, g
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 13

Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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{us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis} : Mortgaged-backed securities (non-government) [Member]
12/31/2010
USD ($)
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12/31/2009
USD ($)
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12/31/2010
USD ($)
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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USD ($)
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12/31/2009
USD ($)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 13

Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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 -Paragraph 1
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12/31/2009
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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 -Name Regulation S-X (SX)
 -Number 210
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 -Paragraph 1
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
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 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
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 -Paragraph 1
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 13

Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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{us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis} : Mortgaged-backed securities (non-government) [Member]
12/31/2010
USD ($)
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12/31/2009
USD ($)
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12/31/2010
USD ($)
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 13

Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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 -Paragraph 1
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12/31/2009
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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 -Name Regulation S-X (SX)
 -Number 210
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 -Paragraph 1
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
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 -Paragraph 1
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 13

Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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{us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis} : Mortgaged-backed securities (non-government) [Member]
12/31/2010
USD ($)
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12/31/2009
USD ($)
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12/31/2010
USD ($)
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12/31/2010
USD ($)
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12/31/2009
USD ($)
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12/31/2008
USD ($)
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 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 13

Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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12/31/2010
USD ($)
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USD ($)
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12/31/2008
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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 -Paragraph 13

Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
 -Article 7

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USD ($)

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12/31/2009
USD ($)

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{us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis} : Hedge funds [Member]
12/31/2010
USD ($)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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 -Paragraph 13

Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 115
 -Paragraph 12
 -Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher SEC
 -Name Regulation S-X (SX)
 -Number 210
 -Section 03
 -Paragraph 1
 -Subparagraph a, f, g
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 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 132R
 -Paragraph 5
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