Fair Value of Financial Instruments (Changes In Fair Value Of Plan's Level 3 Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Interest in Limited Partnerships and Limited Liability Corporations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance, beginning of year	$ 103	$ 129
Realized gains	8	12
Unrealized (losses)	(11)	(5)
Sales and distributions	(8)	(33)
Balance, end of year	$ 92	103
Commingled Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance, beginning of year		33
Realized gains		5
Unrealized (losses)		(5)
Sales and distributions		$ (33)