Investments (excluding Consolidated Investment Entities) - Loans by Debt Service Coverage Ratio (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	$ 6,969	$ 6,879
1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Debt Service Coverage Ratio, minimum	150.00%	150.00%
1.25x - 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Debt Service Coverage Ratio, minimum	125.00%	125.00%
Debt Service Coverage Ratio, maximum	150.00%	150.00%
1.0x - 1.25x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Debt Service Coverage Ratio, minimum	100.00%	100.00%
Debt Service Coverage Ratio, maximum	125.00%	125.00%
1.0x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Debt Service Coverage Ratio, maximum	100.00%	100.00%
Year of Origination 2020
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	$ 227	$ 0
Year of Origination 2020 | 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	167	0
Year of Origination 2020 | 1.25x - 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	35	0
Year of Origination 2020 | 1.0x - 1.25x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	25	0
Year of Origination 2020 | 1.0x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	0
Year of Origination 2020 | Commercial mortgage loans secured by land or construction loans
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	0
Year of Origination 2020 | Total
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	227	0
Year of Origination 2019
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	711	723
Year of Origination 2019 | 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	540	493
Year of Origination 2019 | 1.25x - 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	106	165
Year of Origination 2019 | 1.0x - 1.25x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	65	66
Year of Origination 2019 | 1.0x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	0
Year of Origination 2019 | Commercial mortgage loans secured by land or construction loans
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	0
Year of Origination 2019 | Total
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	711	724
Year of Origination 2018
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	471	513
Year of Origination 2018 | 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	319	351
Year of Origination 2018 | 1.25x - 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	13	13
Year of Origination 2018 | 1.0x - 1.25x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	98	88
Year of Origination 2018 | 1.0x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	41	61
Year of Origination 2018 | Commercial mortgage loans secured by land or construction loans
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	0
Year of Origination 2018 | Total
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	471	513
Year of Origination 2017
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	1,151	1,160
Year of Origination 2017 | 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	623	608
Year of Origination 2017 | 1.25x - 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	272	292
Year of Origination 2017 | 1.0x - 1.25x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	176	167
Year of Origination 2017 | 1.0x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	80	93
Year of Origination 2017 | Commercial mortgage loans secured by land or construction loans
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	0
Year of Origination 2017 | Total
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	1,151	1,160
Year of Origination 2016
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	966	972
Year of Origination 2016 | 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	864	873
Year of Origination 2016 | 1.25x - 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	68	63
Year of Origination 2016 | 1.0x - 1.25x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	30	31
Year of Origination 2016 | 1.0x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	4	4
Year of Origination 2016 | Commercial mortgage loans secured by land or construction loans
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	0
Year of Origination 2016 | Total
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	966	971
Year of Origination 2015
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	799	804
Year of Origination 2015 | 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	744	743
Year of Origination 2015 | 1.25x - 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	49	50
Year of Origination 2015 | 1.0x - 1.25x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	6	6
Year of Origination 2015 | 1.0x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	6
Year of Origination 2015 | Commercial mortgage loans secured by land or construction loans
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	0
Year of Origination 2015 | Total
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	799	805
Year of Origination 2014 and prior
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	2,644	2,707
Year of Origination 2014 and prior | 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	2,232	2,265
Year of Origination 2014 and prior | 1.25x - 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	218	210
Year of Origination 2014 and prior | 1.0x - 1.25x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	123	139
Year of Origination 2014 and prior | 1.0x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	71	92
Year of Origination 2014 and prior | Commercial mortgage loans secured by land or construction loans
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	0
Year of Origination 2014 and prior | Total
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	2,644	2,706
Total | 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	5,489	5,333
Total | 1.25x - 1.5x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	761	793
Total | 1.0x - 1.25x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	523	497
Total | 1.0x
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	196	256
Total | Commercial mortgage loans secured by land or construction loans
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	0	0
Total | Total
Schedule of Loans by Debt Service Coverage Ratio [Line Items]
Commercial mortgage loans	$ 6,969	$ 6,879