SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Changes in Accumulated Other Comprehensive Earnings (Details) - USD ($)	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
COMPREHENSIVE EARNINGS
Tax rate used (as a percent)	21.00%	21.00%
Other comprehensive income (loss), tax	$ (3,500,000)	$ 7,800,000
Changes in the balance of each component of accumulated other comprehensive earnings
Beginning balance	52,473,000
Net current-period other comprehensive earnings (loss)	(13,031,000)	29,301,000
Ending balance	39,464,000
Balance of securities for which an allowance for credit losses has been recognized in net earnings	5,727,000
Reclassification Adjustment Out of Accumulated Other Comprehensive Income
Net realized gains	15,152,000	9,068,000
Credit losses on available-for-sale securities	800,000
Earnings (loss) before income taxes	(79,364,000)	81,741,000
Income tax expense (benefit)	18,097,000	(16,268,000)
Net earnings (loss)	(61,267,000)	65,473,000
Allowance for credit losses	878,000		$ 0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Writeoff	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Recovery	0
Unrealized Gains and Losses on Available-for-Sale Securities
Changes in the balance of each component of accumulated other comprehensive earnings
Beginning balance	52,495,000	(14,572,000)
Other comprehensive earnings before reclassifications	(11,880,000)	29,795,000
Amounts reclassified from accumulated other comprehensive earnings	(1,151,000)	(494,000)
Net current-period other comprehensive earnings (loss)	(13,031,000)	29,301,000
Ending balance	39,464,000	14,729,000
Unrealized Gains and Losses on Available-for-Sale Securities \| Previously Reported
Changes in the balance of each component of accumulated other comprehensive earnings
Beginning balance	52,473,000	(14,572,000)
Unrealized Gains and Losses on Available-for-Sale Securities \| Restatement Adjustment \| Accounting Standards Update 2016-13
Changes in the balance of each component of accumulated other comprehensive earnings
Beginning balance	22,000
Reclassifications out of accumulated other comprehensive earnings \| Unrealized Gains and Losses on Available-for-Sale Securities
Reclassification Adjustment Out of Accumulated Other Comprehensive Income
Net realized gains	2,306,000	625,000
Credit losses on available-for-sale securities	849,000
Earnings (loss) before income taxes	1,457,000	625,000
Income tax expense (benefit)	(306,000)	(131,000)
Net earnings (loss)	$ 1,151,000	$ 494,000

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