Investments - Scheduled Maturities (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Amortized cost
Due in one year or less	$ 1,241
Due after one year through five years	7,933
Due after five years through ten years	7,041
Due after ten years	3,864
Subtotal	20,079
ABS, RMBS and CMBS	585
Amortized cost	20,664	$ 21,057
Fair value
Due in one year or less	1,256
Due after one year through five years	8,126
Due after five years through ten years	7,224
Due after ten years	4,300
Subtotal	20,906
ABS, RMBS and CMBS	635
Fair value	$ 21,541	$ 21,400