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Fair Value Measurement (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 6 Months Ended |  |
--- | --- | --- | ---
Jun. 30, 2013 transfers | Jun. 30, 2012 transfers | Jun. 30, 2013 Minimum [Member] broker | Jun. 30, 2013 Commercial Mortgage Backed Securities [Member] Level 2 [Member] | Dec. 31, 2012 Commercial Mortgage Backed Securities [Member] Level 2 [Member]
Fair Value Measurement [Line Items] |  |  |  |  |
Percentage of portfolio of unadjusted fair values obtained | 98.00% |  |  |  |
Percentage of portfolio of specific unadjusted broker quotes obtained | 2.00% |  |  |  |
Number of knowledgeable outside security brokers consulted to determine fair value |  |  | 1 |  |
Trading securities, fair value disclosure |  |  |  | $ 12.4 | $ 4.3
Transfers between Levels 1, 2, and 3 of the fair value hierarchy | 0 | 0 |  |  |

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- Definition Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 + Details
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