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Fair Value Measurement (Quantitative Information Regarding Level 3 Valuations) (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014
Assets: |  |
Total assets at fair value | $ 3,395,111 | $ 3,752,976
Fair Value, Inputs, Level 3 [Member] | State and municipal bonds [Member] |  |
Assets: |  |
Total assets at fair value | $ 0 | 5,000
Fair Value, Inputs, Level 3 [Member] | State and municipal bonds [Member] | Market Approach Valuation Technique [Member] | Minimum [Member] |  |
Assets: |  |
Comparability Adjustment | 0.00% |
Fair Value, Inputs, Level 3 [Member] | State and municipal bonds [Member] | Market Approach Valuation Technique [Member] | Maximum [Member] |  |
Assets: |  |
Comparability Adjustment | 10.00% |
Fair Value, Inputs, Level 3 [Member] | State and municipal bonds [Member] | Market Approach Valuation Technique [Member] | Weighted Average [Member] |  |
Assets: |  |
Comparability Adjustment | 5.00% |
Fair Value, Inputs, Level 3 [Member] | State and municipal bonds [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] |  |
Assets: |  |
Comparability Adjustment | 0.00% |
Fair Value, Inputs, Level 3 [Member] | State and municipal bonds [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] |  |
Assets: |  |
Comparability Adjustment | 10.00% |
Fair Value, Inputs, Level 3 [Member] | State and municipal bonds [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member] |  |
Assets: |  |
Comparability Adjustment | 5.00% |
Fair Value, Inputs, Level 3 [Member] | Corporate debt, limited observable inputs [Member] |  |
Assets: |  |
Total assets at fair value | $ 14,500 | 13,100
Fair Value, Inputs, Level 3 [Member] | Corporate debt, limited observable inputs [Member] | Market Approach Valuation Technique [Member] | Minimum [Member] |  |
Assets: |  |
Comparability Adjustment | 0.00% |
Fair Value, Inputs, Level 3 [Member] | Corporate debt, limited observable inputs [Member] | Market Approach Valuation Technique [Member] | Maximum [Member] |  |
Assets: |  |
Comparability Adjustment | 5.00% |
Fair Value, Inputs, Level 3 [Member] | Corporate debt, limited observable inputs [Member] | Market Approach Valuation Technique [Member] | Weighted Average [Member] |  |
Assets: |  |
Comparability Adjustment | 2.50% |
Fair Value, Inputs, Level 3 [Member] | Corporate debt, limited observable inputs [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] |  |
Assets: |  |
Comparability Adjustment | 0.00% |
Fair Value, Inputs, Level 3 [Member] | Corporate debt, limited observable inputs [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] |  |
Assets: |  |
Comparability Adjustment | 5.00% |
Fair Value, Inputs, Level 3 [Member] | Corporate debt, limited observable inputs [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member] |  |
Assets: |  |
Comparability Adjustment | 2.50% |
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Securitized Loans and Receivables [Member] |  |
Assets: |  |
Total assets at fair value | $ 800 | $ 4,800
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Securitized Loans and Receivables [Member] | Market Approach Valuation Technique [Member] | Minimum [Member] |  |
Assets: |  |
Comparability Adjustment | 0.00% |
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Securitized Loans and Receivables [Member] | Market Approach Valuation Technique [Member] | Maximum [Member] |  |
Assets: |  |
Comparability Adjustment | 5.00% |
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Securitized Loans and Receivables [Member] | Market Approach Valuation Technique [Member] | Weighted Average [Member] |  |
Assets: |  |
Comparability Adjustment | 2.50% |
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Securitized Loans and Receivables [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] |  |
Assets: |  |
Comparability Adjustment | 0.00% |
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Securitized Loans and Receivables [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] |  |
Assets: |  |
Comparability Adjustment | 5.00% |
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Securitized Loans and Receivables [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member] |  |
Assets: |  |
Comparability Adjustment | 2.50% |

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