Income Taxes (Unaudited) (Details 1) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 115
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%		35.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ (26)	$ (47)
Effective Income Tax Rate Reconciliation, Tax Settlement, Amount		(42)
Effective Income Tax Rate Reconciliation, Increase in Research Tax Credits		(22)
Income Tax Reconciliation, Deduction, Increase in Qualified Production Activity		(15)
Federal and foreign income tax expense	$ 132	$ 138
Effective income tax rate	15.20%	17.50%
Scenario, Forecast [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Tax Adjustments, Settlements, and Unusual Provisions			$ (30)