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 |