Derivatives and Risk Management (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative liabilities		$ 1
Derivative assets	$ 2
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative liabilities	8
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Notional amount	$ 170
Derivative, expiration	Jun. 30, 2020
Derivative assets	$ 2