Fair Value Measurements (Narrative) (Details) (USD $)
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12 Months Ended | ||
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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Fair Value Disclosures [Abstract] | |||
Fair value assets transfers between level 1 and level 2 transfer amount | $ 0 | $ 0 | $ 0 |