Temporarily Impaired Securities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 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	$ 304			$ 134
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(31)			(6)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	26			75
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(23)			(15)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	330			209
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(54)			(21)
Equity Securities, Net Unrealized Gain (Loss)	1	$ 1	$ 6
Equity securities 3	8			15
Equity Securities without Readily Determinable Fair Value, Amount	182			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	69			55
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(9)			(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	(10)			(8)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	76			78
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(19)			(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	235			79
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(22)			(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	19			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	254			131
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (35)			$ (10)