Income Taxes - Additional Information (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal corporate income tax rate, percent		35.00%	21.00%	21.00%	35.00%
Increase to income tax rate provision as a result of Federal corporate tax rate change	[1]		$ 0	$ (31)	$ 865
Unrecognized tax benefit, affect the effective tax rate		$ 13	24	19	13
Accruals for payment of interest and penalties associated with uncertain tax positions		$ 4	10	7	$ 4
Increase (decrease) in accruals for payment of interest and penalties associated with uncertain tax positions			3	3
Net deferred tax asset			$ 1,300	$ 1,386

[1] For 2018, the amount primarily relates to tax return adjustments on certain deferred tax assets impacted by the Federal tax rate change. For 2017, the amount relates to the effects of revaluing our net deferred tax asset for new Tax Legislation that was enacted in December 2017.