SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Guaranteed Living Withdrawal Benefits and Income Taxes (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) subsidiary	Feb. 01, 2015 USD ($)
Income Taxes
Number of subsidiaries not included in federal tax return | subsidiary	1
Guaranteed minimum withdrawal benefits (GMWB) | Annuity account
Guaranteed Minimum Withdrawal Benefits
Decrease in net GMWB liability		$ 266.1
Successor | Guaranteed minimum withdrawal benefits (GMWB) | Annuity account
Guaranteed Minimum Withdrawal Benefits
Net GMWB liability	$ 115.4