Fair Value of Financial Instruments Unobservable Input Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance as of the beginning of the period	$ 151	$ 72	$ 97	$ 88
Net realized and unrealized (gains)/losses	(17)	30	39	14
Transfers out of Level 3 to Level 2		(1)	(2)	(1)
Balance as of the end of the period	134	$ 101	$ 134	$ 101
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	$ 0