Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2018
Income Tax Contingency [Line Items]
Net income tax benefit for provisional remeasurement of certain deferred taxes and related amounts	$ (77)
Provisional of income tax expense for estimated effects of transition tax, net of adjustments related to uncertain tax positions	$ 212
Forecast [Member]
Income Tax Contingency [Line Items]
Corporate income tax blended rate		24.50%