Derivatives And Risk Management (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative liabilities	$ 2	$ 3
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative liabilities	2
Notional amount	$ 170
Derivative, expiration	Jun. 30, 2020
Natural Gas [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative liabilities	$ 23