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Investments - Bank loans amortized cost by credit quality and year of acquisition (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Schedule of Available for Sale Securities
Mortgage loans, net	$ 4,075	$ 4,817
Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	1,085
Allowance	(67)
Mortgage loans, net	1,018
2015 and prior \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	38
2016 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	41
2017 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	193
2018 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	256
2019 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	263
Current \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	294
BBB \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	43
BBB \| 2015 and prior \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	0
BBB \| 2016 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	0
BBB \| 2017 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	9
BBB \| 2018 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	7
BBB \| 2019 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	14
BBB \| Current \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	13
BB \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	212
BB \| 2015 and prior \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	20
BB \| 2016 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	2
BB \| 2017 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	25
BB \| 2018 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	58
BB \| 2019 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	53
BB \| Current \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	54
B \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	607
B \| 2015 and prior \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	11
B \| 2016 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	23
B \| 2017 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	115
B \| 2018 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	141
B \| 2019 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	122
B \| Current \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	195
CCC and below \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	223
CCC and below \| 2015 and prior \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	7
CCC and below \| 2016 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	16
CCC and below \| 2017 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	44
CCC and below \| 2018 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	50
CCC and below \| 2019 \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	74
CCC and below \| Current \| Bank loans
Schedule of Available for Sale Securities
Amortized cost before allowance	$ 32