CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net income	$ 51,559,000	$ 88,677,000	$ 21,673,000
Other comprehensive income, net of reclassifications into net income:
Change in net unrealized gains (losses) during the year	27,662,000	(13,223,000)	2,617,000
Reclassification adjustments for gains included in income		(41,000)	(2,231,000)
Reclassification adjustments for foreign currency translation gains			216,000
Amortization of losses previously held as available-for-sale	30,000	99,000	34,000
Other comprehensive income (loss)	27,692,000	(13,165,000)	636,000
Income tax expense (benefit) related to items of other comprehensive income (loss) Securities available-for-sale:
Change in net unrealized gains (losses) during the year	7,469,000	(3,570,000)	1,046,000
Reclassification adjustments for gains included in income		(11,000)	(892,000)
Amortization of losses previously held as available-for-sale	8,000	27,000	14,000
Income tax expense (benefit) related to items of other comprehensive income (loss)	7,477,000	(3,554,000)	168,000
Other comprehensive income (loss), net of tax and reclassifications into net income	20,215,000	(9,611,000)	468,000
Comprehensive income	$ 71,774,000	$ 79,066,000	$ 22,141,000