Net Earnings Per Common Share (Basic And Diluted Net Earnings Per Common Share Based On The Weighted Average Outstanding Shares) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	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
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 124	$ 161	$ 168	$ 139	$ 137	$ 127	$ 114	$ 91	$ 592	$ 469	$ 309
Less common and preferred dividends, Basic									(131)	(115)	(108)
Undistributed Earnings, Diluted									461	354	201
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic									4	4	2
Undistributed earnings (loss) applicable to nonvested shares, Basic									457	350	199
Distributed earnings applicable to common shares, Basic									(88)	(57)	(45)
Net earnings (loss) applicable to common shareholders									$ 545	$ 407	$ 244
Weighted average common shares outstanding									200,776	203,855	203,265
Net earnings (loss) per common share, Basic	$ 0.57	$ 0.75	$ 0.76	$ 0.63	$ 0.61	$ 0.57	$ 0.44	$ 0.38	$ 2.71	$ 2.00	$ 1.20
Additional weighted average dilutive shares, Diluted									8,877	414	433
Weighted average diluted common shares outstanding, Diluted									209,653	204,269	203,698
Net earnings (loss) per common share, Diluted	$ 0.54	$ 0.72	$ 0.73	$ 0.61	$ 0.60	$ 0.57	$ 0.44	$ 0.38	$ 2.60	$ 1.99	$ 1.20