SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Changes in Accumulated Other Comprehensive Earnings (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
COMPREHENSIVE EARNINGS
Tax rate used (as a percent)	35.00%	35.00%	35.00%
Other comprehensive income (loss), tax	$ (600)	$ (25,300)	$ 19,000
Changes in the balance of each component of accumulated other comprehensive earnings
Beginning balance	123,774
Net current-period other comprehensive earnings (loss)	(1,164)	(47,609)	35,356
Ending balance	122,610	123,774
Unrealized Gains and Losses on Available-for-Sale Securities
Changes in the balance of each component of accumulated other comprehensive earnings
Beginning balance	123,774	171,383	136,027
Other comprehensive earnings before reclassifications	26,740	(26,199)	57,081
Amounts reclassified from accumulated other comprehensive earnings	(27,904)	(21,410)	(21,725)
Net current-period other comprehensive earnings (loss)	(1,164)	(47,609)	35,356
Ending balance	$ 122,610	$ 123,774	$ 171,383

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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