Income Taxes Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Income Tax Disclosure [Abstract]
Other Tax Expense (Benefit)	$ 275
Expected Deferred Tax Asset Liability Reversal Rate	21.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 285
Other Tax Expense Benefit Transition Tax	561
TransitionTaxPayableAcquiree	220
Transition Tax Estimated To Be Payable	$ 781