Common Stock And Share-Based Compensation (Performance Shares) (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average period (years)		1 year 5 months 1 day
Performance Shares, Equity Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee service share based compensation nonvested performance shares total compensation cost not yet recognized		$ 46
Nonvested at January 1, Number of Performance Shares		1,838,855
Granted, Number of Performance Shares		745,724
Vested, Number of Performance Shares		(81,501)
Forfeited, Number of Performance Shares	[1]	(755,050)
Nonvested at December 31, Number of Performance Shares		1,748,028	1,838,855
Nonvested at January 1, Weighted Average Exercise Price		$ 58.65
Granted, Weighted Average Exercise Price		77.00	$ 53.61	$ 68.27
Vested, Weighted Average Exercise Price		53.74
Forfeited, Weighted Average Exercise Price		66.30
Nonvested at December 31, Weighted Average Exercise Price		$ 63.40	$ 58.65

[1] Includes performance shares that expired with zero value as performance targets were not met.