Income Taxes Textuals (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Income Taxes (Textuals) [Line Items]
U.S. Tax Act Discrete Tax (Benefit) charge		$ 24
Effective tax rate	13.40%	(19.40%)
Reduction in Effective Tax Rate		22.20%
Income Tax Contingency [Line Items]
Open tax years by major tax jurisdiction	2015
Internal Revenue Service (IRS) [Member] | Earliest Year [Member]
Income Tax Contingency [Line Items]
Open tax years by major tax jurisdiction	2015
Tax Audit Settlement Years			2008
Internal Revenue Service (IRS) [Member] | Latest Year [Member]
Income Tax Contingency [Line Items]
Tax Audit Settlement Years			2014