Net Income Per Common Share (Basic And Diluted Net Income Per Common Share) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Net income	$ 117	$ 147	$ 143	$ 134	$ 130	$ 117	$ 144	$ 130	$ 541	$ 521	$ 393
Income allocated to participating securities	2	2	2	2	2	1	2	1	8	6	4
Net income attributable to common shares	$ 115	$ 145	$ 141	$ 132	$ 128	$ 116	$ 142	$ 129	$ 533	$ 515	$ 389
Basic average common shares									183	191	185
Basic earnings per common share	$ 0.64	$ 0.80	$ 0.77	$ 0.71	$ 0.68	$ 0.61	$ 0.73	$ 0.66	$ 2.92	$ 2.68	$ 2.11
Basic average common shares									183	191	185
Net effect of the assumed exercise of stock options									1	1	0
Net effect of the assumed exercise of warrants									3	0	1
Diluted average common shares									187	192	186
Diluted earnings per common share	$ 0.62	$ 0.78	$ 0.76	$ 0.70	$ 0.68	$ 0.61	$ 0.73	$ 0.66	$ 2.85	$ 2.67	$ 2.09