OTHER COMPREHENSIVE INCOME (LOSS) - Component of other comprehensive income (loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Before tax amount
Other comprehensive income (loss), before tax amount	$ (404,757)	$ 273,508	$ 384,298
Income tax (expense) benefit
Other comprehensive income (loss), tax (expense) benefit	46,898	(30,823)	(35,478)
Net of tax amount
Other comprehensive income (loss), net of tax amount	(357,859)	242,685	348,820
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized
Before tax amount
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized	(310,710)	360,357
Income tax (expense) benefit
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized	39,263	(43,191)
Net of tax amount
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized	(271,447)	317,166
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has been recognized
Before tax amount
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized	81	(40)
Income tax (expense) benefit
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized	0	0
Net of tax amount
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized	81	(40)
Unrealized gains (losses) on available for sale investments, net of tax:
Before tax amount
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized			414,982
Adjustment for reclassification of net realized (gains) losses and impairment losses recognized in net income (loss)	(94,749)	(90,380)	(29,618)
Other comprehensive income (loss), before tax amount	(405,378)	269,937	385,364
Income tax (expense) benefit
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized			(40,367)
Adjustment for reclassification of net realized (gains) losses and impairment losses recognized in net income (loss)	7,635	12,368	4,889
Other comprehensive income (loss), tax (expense) benefit	46,898	(30,823)	(35,478)
Net of tax amount
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized			374,615
Adjustment for reclassification of net realized (gains) losses and impairment losses recognized in net income (loss)	(87,114)	(78,012)	(24,729)
Other comprehensive income (loss), net of tax amount	(358,480)	239,114	349,886
Foreign currency translation adjustment
Before tax amount
Other comprehensive income (loss), before tax amount	621	3,571	(1,066)
Income tax (expense) benefit
Other comprehensive income (loss), tax (expense) benefit	0	0	0
Net of tax amount
Other comprehensive income (loss), net of tax amount	$ 621	$ 3,571	$ (1,066)