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Investments Investments - Bank loans amortized cost by credit quality and year of acquisition (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Schedule of Available for Sale Securities
Amortized cost, net	$ 4,655	$ 4,817
Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	1,101
Allowance	(61)
Amortized cost, net	1,040
2015 and prior \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	43
2016 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	44
2017 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	206
2018 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	290
2019 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	284
Current \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	234
BBB \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	44
BBB \| 2015 and prior \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	0
BBB \| 2016 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	0
BBB \| 2017 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	9
BBB \| 2018 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	9
BBB \| 2019 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	14
BBB \| Current \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	12
BB \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	237
BB \| 2015 and prior \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	30
BB \| 2016 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	2
BB \| 2017 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	37
BB \| 2018 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	58
BB \| 2019 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	58
BB \| Current \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	52
B \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	610
B \| 2015 and prior \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	6
B \| 2016 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	33
B \| 2017 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	116
B \| 2018 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	168
B \| 2019 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	138
B \| Current \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	149
CCC and below \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	210
CCC and below \| 2015 and prior \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	7
CCC and below \| 2016 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	9
CCC and below \| 2017 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	44
CCC and below \| 2018 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	55
CCC and below \| 2019 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	74
CCC and below \| Current \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	$ 21