Income Taxes - Income Tax Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Operating loss carryforwards	$ 529
Valuation allowance	520	$ 77
Provisional benefit of revaluation of net DTL due to TCJA		$ 1,500
Benefit of revaluation of net DTL due to TCJA	$ 100

Tax Cuts and Jobs Act, Change in Tax Rate, Income Tax Expense (Benefit)

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- Definition

Tax Cuts and Jobs Act, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit)

+ References

No definition available.

+ Details

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- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

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- References

No definition available.

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- Definition

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

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