SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Effect of New Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Balance Sheet
Deferred policy acquisition costs and value of business acquired	$ 2,974,293		$ 2,974,293		$ 2,199,577
Other liabilities	2,575,056		2,575,056		$ 2,353,565
Statements of Income
Other income	113,530	$ 110,970	341,802	$ 331,523
Amortization of deferred policy acquisition costs and value of business acquired	33,511	3,991	144,009	47,612
Other operating expenses, net of reinsurance ceded	224,585	$ 225,613	684,907	$ 674,236
Before ASC 606
Balance Sheet
Deferred policy acquisition costs and value of business acquired	2,832,400		2,832,400
Other liabilities	2,308,700		2,308,700
Statements of Income
Other income	115,100		345,300
Amortization of deferred policy acquisition costs and value of business acquired	21,700		107,300
Other operating expenses, net of reinsurance ceded	$ 237,700		$ 725,100