Stockholders' Equity (Summary Of Dividends Paid On Common Stock) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015
Stockholders Equity Note [Abstract]
Common stock dividends paid, Amount	$ 32	$ 33	$ 125	$ 99	$ 98	$ 99	$ 190	$ 296
Common stock dividends, rate per share	$ 0.06	$ 0.06	$ 0.24	$ 0.24	$ 0.24	$ 0.24