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Fair Value Measurement (Narrative) (Details) $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 30, 2015 USD ($) transfers broker | Jun. 30, 2014 transfers | Dec. 31, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Percentage of portfolio of unadjusted fair values obtained | 99.60% |  |
Percentage of portfolio of specific unadjusted broker quotes obtained | 0.40% |  |
Transfers between Levels 1, 2, and 3 of the fair value hierarchy | 0 | 0 |
Commercial Mortgage Backed Securities [Member] | Level 2 [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Trading securities, fair value disclosure | $ | $ 45.2 |  | $ 32.5
Minimum [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Number of knowledgeable outside security brokers consulted to determine fair value | broker | 1 |  |

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