Temporarily Impaired Securities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 224			$ 134
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(21)			(6)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	30			75
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(22)			(15)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	254			209
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(43)			(21)
Equity Securities, Net Unrealized Gain (Loss)	(1)	$ 1	$ 7
Equity securities 3	8			15
Equity Securities without Readily Determinable Fair Value, Amount	184			189
US Treasury and Government [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	66			55
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(6)			(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	7			23
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(9)			(8)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	73			78
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(15)			(11)
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	158			79
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(15)			(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	23			52
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(13)			(7)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	181			131
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (28)			$ (10)