Accounting Policies (Details) $ in Millions	Dec. 31, 2017 USD ($)
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 9
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease Liability Expected	100
Operating Lease Right Of Use Asset Expected	$ 100