CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS - Activity During Period (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	Dec. 31, 2017	Dec. 31, 2016
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Separate account balances					$ 13,956,071	$ 13,244,252
Annuity account | CALIC
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Average attained age of contract holders			67 years
Percentage of variable annuity business reinsured			100.00%
Annuity account | Acquisitions | CALIC
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Guaranteed amount payable					8,400
Guaranteed minimum death benefits (GMDB)
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Separate account balances					$ 9,700,000
Guaranteed minimum death benefits (GMDB) | Annuity account
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Interest rate at which last anniversary date account value is compounded (as a percent)					5.00%
Separate account balances					$ 13,100,000
Mean investment performance (as a percent)					7.01%
Average discount rate (as a percent)					4.90%
Guaranteed amount payable					$ 90,500
Guaranteed amount payable with GMDB reserve	$ 29,010	$ 36,427	$ 34,796	$ 36,427	34,030	$ 34,796
Average attained age of contract holders			73 years
Activity relating to GMDB reserves (excluding those 100% reinsured under the Modco agreement)
Balance at the beginning of the period		29,010	$ 34,796	36,427
Incurred guarantee benefits		10,175	849	678
Less: Paid guarantee benefits		2,758	1,615	2,309
Balance at the end of the period	29,010	36,427	34,030	$ 34,796
Guaranteed minimum death benefits (GMDB) | Annuity account | Annuities
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Guaranteed amount payable					72,800
Guaranteed amount payable with GMDB reserve			30,900		30,900
Activity relating to GMDB reserves (excluding those 100% reinsured under the Modco agreement)
Balance at the end of the period			30,900
Guaranteed minimum death benefits (GMDB) | Annuity account | Acquisitions
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Guaranteed amount payable					17,700
Guaranteed amount payable with GMDB reserve			3,100		$ 3,100
Activity relating to GMDB reserves (excluding those 100% reinsured under the Modco agreement)
Balance at the end of the period			$ 3,100
Predecessor | Guaranteed minimum death benefits (GMDB) | Annuity account
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Guaranteed amount payable with GMDB reserve	26,251	28,875
Activity relating to GMDB reserves (excluding those 100% reinsured under the Modco agreement)
Balance at the beginning of the period	26,251	$ 28,875
Incurred guarantee benefits	3,073
Less: Paid guarantee benefits	449
Balance at the end of the period	$ 28,875