Shareholders' Equity And Net Income Per Share Dividends (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended								12 Months Ended
	Nov. 22, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends Payable [Line Items]
Payments of Cash Dividends		$ 77	$ 77	$ 78	$ 78	$ 79	$ 79	$ 79	$ 80	$ 310	$ 317
Common Stock, Dividends, Per Share, Cash Paid		$ 0.29	$ 0.29	$ 0.29	$ 0.29	$ 0.29	$ 0.29	$ 0.29	$ 0.29	$ 1.16	$ 1.16
Cash dividends declared per share		$ 0.22								$ 1.38	$ 1.16	$ 1
Record Date	Nov. 22, 2017