Accounting Pronouncements Adoption of New Accounting Pronouncements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019
Accounting Standards Update 2016-02 - Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Assets			$ 2,000
Operating Lease, Liabilities			$ 2,000
Other Expense [Member] | Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 33	$ 26