SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Effect of New Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Balance Sheet
Deferred policy acquisition costs and value of business acquired	$ 2,870,620		$ 2,870,620		$ 2,199,577
Other liabilities	2,535,106		2,535,106		$ 2,353,565
Statements of Income
Other income	113,861	$ 111,311	228,272	$ 220,553
Amortization of deferred policy acquisition costs and value of business acquired	52,517	23,102	110,498	43,621
Other operating expenses, net of reinsurance ceded	231,071	$ 225,836	460,322	$ 448,623
Before ASC 606
Balance Sheet
Deferred policy acquisition costs and value of business acquired	2,729,900		2,729,900
Other liabilities	2,270,300		2,270,300
Statements of Income
Other income	117,000		230,200
Amortization of deferred policy acquisition costs and value of business acquired	41,400		85,600
Other operating expenses, net of reinsurance ceded	$ 243,900		$ 487,400