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Investments (Details 3) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 | Dec. 31, 2016
Estimated expected maturity: |  |
Due in 1 year or less, Percent of Total Fair Value | 3.80% | 3.90%
Due in 1 year or less, Fair Value | $ 284,164 |
Due in 1 year or less, Amortized Cost | $ 271,394 |
Due after 1 year through 5 years, Percent of Total Fair Value | 28.10% | 28.70%
Due after 1 year through 5 years, Fair Value | $ 2,109,683 |
Due after 1 year through 5 years, Amortized Cost | $ 2,014,879 |
Due after 5 years through 10 years, Percent of Total Fair Value | 34.10% | 35.20%
Due after 5 years through 10 years, Fair Value | $ 2,562,229 |
Due after 5 years through 10 years, Amortized Cost | $ 2,447,089 |
Due after 10 years through 20 years, Percent of Total Fair Value | 21.10% | 19.50%
Due after 10 years through 20 years, Fair Value | $ 1,582,732 |
Due after 10 years through 20 years, Amortized Cost | $ 1,511,608 |
Due after 20 years, Percent of Total Fair Value | 12.90% | 12.70%
Due after 20 years, Fair Value | $ 971,942 |
Due after 20 years, Amortized Cost | $ 928,265 |
Total, Percent of Total Fair Value | 100.00% | 100.00%
Total, Fair Value | $ 7,510,750 | $ 7,456,708
Total, Amortized Cost | $ 7,173,235 | $ 7,152,127
Average option-adjusted duration, in years | 6 years | 5 years 10 months 24 days

X
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- Definition Amount of available-for-sale debt securities at cost, net of adjustments, maturing after the twentieth rolling twelve months following the latest balance sheet presented. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, defined) and fair value hedge accounting adjustments. + References No definition available. + Details
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