Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Dec. 31, 2017	Jun. 30, 2018
Income Tax Disclosure [Abstract]
U.S. tax reform provisional income tax charge	$ 3,100
Investments, Owned, Federal Income Tax Note [Line Items]
Deferred tax liability as a percentage of indefinitely reinvested earnings		24.00%
Minimum
Investments, Owned, Federal Income Tax Note [Line Items]
Foreign earnings expected to be indefinitely reinvested		$ 200
Maximum
Investments, Owned, Federal Income Tax Note [Line Items]
Foreign earnings expected to be indefinitely reinvested		$ 300