INVESTMENT OPERATIONS - Summary of Change in Unrealized Gains (Losses), Net of Income Tax, on Fixed Maturity and Equity Securities Classified as Available-for-Sale (Details) - USD ($) $ in Thousands	1 Months Ended	11 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Fixed maturities
Investment [Line Items]
Change in unrealized gains (losses) net of income tax		$ (1,874,469)	$ 1,086,727	$ 802,368
Equity securities
Investment [Line Items]
Change in unrealized gains (losses) net of income tax		$ 4,406	$ 17,863	$ (13,463)
Predecessor | Fixed maturities
Investment [Line Items]
Change in unrealized gains (losses) net of income tax	$ 670,229
Predecessor | Equity securities
Investment [Line Items]
Change in unrealized gains (losses) net of income tax	$ 10,226