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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - AOCI (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Accumulated other comprehensive income (loss) |  |  |
Beginning Balance | $ 677,055 |  |
Adjust funded status of pension plan, net of tax of $0.0, $0.7 and $0.7 million for the years December 31, 2017, 2016 and 2015 respectively | 1,357 | $ 5,251 | $ (809)
Foreign currency translation adjustment | 1,265 | (687) | 26
Reclassifications of gains on sale of marketable securities to net income | (1,044) |  |
Unrealized gain on securities | 440 | 868 |
Ending Balance | 688,727 | 677,055 |
Adjust funded status of pension plan, tax | 700 | 700 | 700
Accumulated Other Comprehensive Income/(Loss) |  |  |
Accumulated other comprehensive income (loss) |  |  |
Beginning Balance | 1,728 | (3,704) | (2,921)
Adjust funded status of pension plan, net of tax of $0.0, $0.7 and $0.7 million for the years December 31, 2017, 2016 and 2015 respectively | 1,357 | 5,251 | (809)
Foreign currency translation adjustment | 1,265 | (687) | 26
Reclassifications of gains on sale of marketable securities to net income | (1,044) |  |
Unrealized gain on securities | 440 | 868 |
Ending Balance | 3,746 | 1,728 | (3,704)
Pension and other postretirement benefit plans |  |  |
Accumulated other comprehensive income (loss) |  |  |
Beginning Balance | 1,770 | (3,481) | (2,672)
Adjust funded status of pension plan, net of tax of $0.0, $0.7 and $0.7 million for the years December 31, 2017, 2016 and 2015 respectively | 1,357 | 5,251 | (809)
Ending Balance | 3,127 | 1,770 | (3,481)
Translation Adjustment |  |  |
Accumulated other comprehensive income (loss) |  |  |
Beginning Balance | (910) | (223) | (249)
Foreign currency translation adjustment | 1,265 | (687) | 26
Ending Balance | 355 | (910) | $ (223)
Investment |  |  |
Accumulated other comprehensive income (loss) |  |  |
Beginning Balance | 868 |  |
Reclassifications of gains on sale of marketable securities to net income | (1,044) |  |
Unrealized gain on securities | 440 | 868 |
Ending Balance | $ 264 | $ 868 |

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