Income Taxes - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal corporate income tax rate, percent	35.00%	21.00%	35.00%	35.00%
Increase to income tax rate provision as a result of Federal corporate tax rate change		$ (31)	$ 865	$ 0
Unrecognized tax benefit, affect the effective tax rate	$ 13	19	13	10
Accruals for payment of interest and penalties associated with uncertain tax positions	4	7	4	$ 3
Increase (decrease) in accruals for payment of interest and penalties associated with uncertain tax positions	1	3	1
Net deferred tax asset	$ 1,540	$ 1,386	$ 1,540

Unrecognized Tax Benefits, Increase (Decrease) in Income Tax Penalties and Interest Accrued

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- Definition

Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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- Definition

The amount of estimated penalties and interest accrued as of the balance sheet date arising from income tax examinations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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