Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at beginning of period	$ 970	$ 21
Tax positions of prior periods netted against deferred tax assets	(24)
Tax positions of prior periods netted against deferred tax assets		950
(Decrease) increase in tax positions taken in the prior period	1
(Decrease) increase in tax positions taken in the prior period		(1)
Increase in tax positions taken in the current period	5	3
Decrease due to settlement/payments	0	(1)
Decrease from the lapse of statute of limitations	0	(2)
Unrecognized tax benefits at end of period	$ 952	$ 970