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INVESTMENTS (Tables) | 6 Months Ended
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Jun. 30, 2017
INVESTMENTS |
Summary of investments in available-for-sale |
June 30, 2017 |  | Amortized Cost |  | Gross Unrealized Holding Gains |  | Gross Unrealized Holding Losses |  | Fair Value |  | Continuous Unrealized Loss Position less than 12 Months |  | Continuous Unrealized Loss Position greater than 12 Months
Available-for-sale |  |  |  |  |  |  |  |  |  |  |  |
Short-term: |  |  |  |  |  |  |  |  |  |  |  |
Commercial paper |  | $ | 73,037 |  | $ | 3 |  | $ | - |  | $ | 73,040 |  | $ | - |  | $ | -
Certificates of deposit |  | 37,210 |  | - |  | - |  | 37,210 |  | - |  | -
Municipal securities |  | 152,287 |  | 8 |  | 42 |  | 152,253 |  | 42 |  | -
U.S. government agency securities |  | 28,465 |  | - |  | 22 |  | 28,443 |  | 22 |  | -
Variable rate demand notes |  | 32,905 |  | - |  | - |  | 32,905 |  | - |  | -
Long-term: |  |  |  |  |  |  |  |  |  |  |  |
Municipal securities |  | 32,704 |  | - |  | 17 |  | 32,687 |  | 17 |  | -
U.S. government agency securities |  | 15,974 |  | - |  | 22 |  | 15,952 |  | 22 |  | -
Total |  | $ | 372,582 |  | $ | 11 |  | $ | 103 |  | $ | 372,490 |  | $ | 103 |  | $ | -
December 31, 2016 |  | Amortized Cost |  | Gross Unrealized Holding Gains |  | Gross Unrealized Holding Losses |  | Fair Value |  | Continuous Unrealized Loss Position less than 12 Months |  | Continuous Unrealized Loss Position greater than 12 Months
Available-for-sale |  |  |  |  |  |  |  |  |  |  |  |
Short-term: |  |  |  |  |  |  |  |  |  |  |  |
Commercial paper |  | $ | 40,382 |  | $ | - |  | $ | - |  | $ | 40,382 |  | $ | - |  | $ | -
Municipal securities |  | 140,379 |  | - |  | 181 |  | 140,198 |  | 181 |  | -
U.S. government agency securities |  | 26,057 |  | - |  | 6 |  | 26,051 |  | 6 |  | -
Variable rate demand notes |  | 13,923 |  | - |  | - |  | 13,923 |  | - |  | -
Long-term: |  |  |  |  |  |  |  |  |  |  |  |
Municipal securities |  | 2,403 |  | - |  | 9 |  | 2,394 |  | 9 |  | -
Total |  | $ | 223,144 |  | $ | - |  | $ | 196 |  | $ | 222,948 |  | $ | 196 |  | $ | -
Summarizes the underlying contractual maturities of the Company's investments |
|  | June 30, 2017 |  | December 31, 2016
|  | Amortized Cost |  | Fair Value |  | Amortized Cost |  | Fair Value
Less than 1 year: |  |  |  |  |  |  |  |
Commercial paper |  | $ | 73,037 |  | $ | 73,040 |  | $ | 40,382 |  | $ | 40,382
Certificates of deposit |  | 37,210 |  | 37,210 |  | - |  | -
Municipal securities |  | 152,287 |  | 152,253 |  | 140,379 |  | 140,198
U.S. government agency securities |  | 28,465 |  | 28,443 |  | 26,057 |  | 26,051
Due 1 -10 years: |  |  |  |  |  |  |  |
Municipal securities |  | 32,704 |  | 32,687 |  | 2,403 |  | 2,394
U.S. government agency securities |  | 15,974 |  | 15,952 |  | - |  | -
Variable rate demand notes |  | 3,918 |  | 3,918 |  | 3,917 |  | 3,917
Due 11 - 20 years: |  |  |  |  |  |  |  |
Variable rate demand notes |  | 10,006 |  | 10,006 |  | 6,003 |  | 6,003
Due 21 - 30 years: |  |  |  |  |  |  |  |
Variable rate demand notes |  | 14,979 |  | 14,979 |  | 4,003 |  | 4,003
Due 31 - 40 years: |  |  |  |  |  |  |  |
Variable rate demand notes |  | 4,002 |  | 4,002 |  | - |  | -
Total |  | $ | 372,582 |  | $ | 372,490 |  | $ | 223,144 |  | $ | 222,948

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