CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS - Activity During Period (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Separate account balances				$ 12,377,571	$ 12,730,090
Guaranteed amount payable with GMDB reserve	$ 37,700	$ 37,700		34,100	37,700
Activity relating to GMDB reserves (excluding those 100% reinsured under the Modco agreement)
Beginning balance	37,700
Ending balance	$ 34,100	$ 37,700
Annuity account | CALIC
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Average attained age of contract holders	69 years	68 years
Percentage of variable annuity business reinsured	100.00%
Annuity account | Acquisitions | CALIC
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Guaranteed amount payable				$ 6,400	7,100
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				$ 14,800,000	12,200,000
Mean investment performance (as a percent)				6.20%
Average discount rate (as a percent)				4.50%
Guaranteed amount payable				$ 177,600	116,100
Guaranteed amount payable with GMDB reserve	$ 37,684	$ 37,684	$ 26,934	34,071	37,684
Average attained age of contract holders	72 years	68 years
Activity relating to GMDB reserves (excluding those 100% reinsured under the Modco agreement)
Beginning balance	$ 37,684	$ 34,700	26,934
Great West beginning balance	0	7,457	0
Incurred guarantee benefits	1,184	(809)	11,065
Less: Paid guarantee benefits	4,797	3,664	3,299
Ending balance	$ 34,071	$ 37,684	$ 34,700
Guaranteed living withdrawal benefits (GLWB) | Annuity account
CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS
Separate account balances				$ 8,900,000	$ 8,400,000