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	$ 2,875,743		$ 2,875,743		$ 2,205,401
Other liabilities	2,087,057		2,087,057		$ 1,859,254
Statements of Income
Other income	79,754	$ 82,087	160,428	$ 161,470
Amortization of deferred policy acquisition costs and value of business acquired	52,630	23,454	110,703	44,238
Other operating expenses, net of reinsurance ceded	195,260	$ 195,079	392,413	$ 385,557
Before ASC 606
Balance Sheet
Deferred policy acquisition costs and value of business acquired	2,737,600		2,737,600
Other liabilities	1,829,800		1,829,800
Statements of Income
Other income	82,800		162,500
Amortization of deferred policy acquisition costs and value of business acquired	41,800		86,200
Other operating expenses, net of reinsurance ceded	$ 207,800		$ 419,100