Description Of Business And Basis Of Presentation Description of Business and Basis of Presentation (Impact of Recently Adopted Accounting Standards) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2017	Dec. 31, 2017
Accounting Standards Update 2016-09 [Member]
Change in Accounting Estimate [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax	$ 8
Minimum
Change in Accounting Estimate [Line Items]
Cumulative Effect on Retained Earnings, before Tax		$ 600
Maximum
Change in Accounting Estimate [Line Items]
Cumulative Effect on Retained Earnings, before Tax		$ 800