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Investments Investments - Bank loans amortized cost by credit quality and year of acquisition (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Schedule of Available for Sale Securities
Amortized cost, net	$ 4,774	$ 4,817
Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	1,194
Allowance	(76)
Amortized cost, net	1,118
2015 and prior \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	51
2016 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	68
2017 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	233
2018 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	359
2019 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	305
Current \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	178
BBB \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	43
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	13
BBB \| 2019 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	9
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	241
BB \| 2015 and prior \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	31
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	36
BB \| 2018 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	72
BB \| 2019 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	64
BB \| Current \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	36
B \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	684
B \| 2015 and prior \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	12
B \| 2016 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	34
B \| 2017 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	142
B \| 2018 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	219
B \| 2019 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	173
B \| Current \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	104
CCC and below \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	226
CCC and below \| 2015 and prior \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	8
CCC and below \| 2016 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	32
CCC and below \| 2017 \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	46
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	59
CCC and below \| Current \| Bank loans, net
Schedule of Available for Sale Securities
Amortized cost before allowance	$ 26