Income Taxes And Tax-Related Items Reconciliation of the Beginning and Ending Amounts of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance at January 1	$ 15	$ 22	$ 14
Increases as a result of tax positions taken during a prior period	4	0	8
Decrease related to settlements with tax authorities	(8)	(7)	0
Decrease related to other tax position changes	(1)	0	0
Balance at December 31	$ 10	$ 15	$ 22