Fair Value of Financial Instruments Unobservable Input Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance as of the beginning of the period	$ 134	$ 70	$ 97	$ 88
Net realized and unrealized (gains)/losses	17	3	56	(16)
Transfers out of Level 3 to Level 2		(1)	(2)	0
Balance as of the end of the period	151	$ 72	$ 151	$ 72
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	$ 0