BUSINESS SEGMENT INFORMATION - Reconciliation of Revenue from Segments to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 1,840	$ (2,550)	$ 12,609	$ 3,078	$ 3,156	$ 1,709	$ 10,059	$ 4,865	$ 11,899	$ 7,943	$ 9,619	$ 12,069	$ 12,430
Operating Segments | Individual Retirement
Segment Reporting Information [Line Items]
Total revenues	1,079			1,181					3,352	3,253
Operating Segments | Group Retirement
Segment Reporting Information [Line Items]
Total revenues	301			273					829	791
Operating Segments | Investment Management and Research
Segment Reporting Information [Line Items]
Total revenues	899			872					2,650	2,500
Operating Segments | Protection Solutions
Segment Reporting Information [Line Items]
Total revenues	751			855					2,344	2,524
Corporate and Other
Segment Reporting Information [Line Items]
Total revenues	300			302					881	914
Adjustments
Adjustments related to:
Variable annuity product features	(1,512)			(608)					1,160	(2,244)
Investment (gains) losses	17			199					190	176
Other adjustments to segment revenues	5			4					493	29
Assumption updates due to COVID-19									46
Other COVID-19 related impact									(30)
Intersegment Eliminations
Adjustments related to:
Investment expenses	17			18					51	57
Investment management and other fees | Intersegment Eliminations
Adjustments related to:
Revenues	$ 28			$ 26					$ 82	$ 77