Quarterly Results of Operations (Unaudited) Quarterly Results of Operations (Unaudited) (Narrative) (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Accounting Changes and Error Corrections [Abstract]
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)	$ 882

Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)

No definition available.

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