Investments - Scheduled maturities of available for sale fixed maturities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Fair Value Percent, Fiscal Year Maturity [Abstract]
Average life of ABS	4 years 6 months
Average life of MBS	4 years 6 months
Fixed maturities
Amortized Cost Basis, Fiscal Year Maturity [Abstract]
One year or less	$ 1,549
After one year through five years	9,016
After five years through ten years	14,097
After ten years	4,470
Fixed maturities amortized cost, Subtotal	29,132
ABS (average life of approximately 4.5 years)	9,909
MBS (average life of approximately 4.5 years)	3,377
Amortized Cost	42,418
Fair Value, Fiscal Year Maturity [Abstract]
One year or less	1,561
After one year through five years	9,177
After five years through ten years	14,384
After ten years	4,611
Fixed maturities fair value, Subtotal	29,733
ABS (average life of approximately 4.5 years)	10,018
MBS (average life of approximately 4.5 years)	3,680
Fair Value	$ 43,431
Fair Value Percent, Fiscal Year Maturity [Abstract]
One year or less	4.00%
After one year through five years	21.00%
After five years through ten years	33.00%
After ten years	11.00%
Fixed maturities fair value, Subtotal, Percent	69.00%
ABS (average life of approximately 4.5 years)	23.00%
MBS (average life of approximately 4.5 years)	8.00%
Fair value, Total, Percent	100.00%