Retirement And Employee Benefit Plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Contribution expense	$ 3	$ 3	$ 2
Contributions capitalized	3	3	3
Net actuarial loss arising during the year	25
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	12	14	11
Change in accumulated other comprehensive income (loss)	(23)	19
Change in accumulated other comprehensive income (loss) after tax	(14)	12
Net actuarial loss arising during the year	(23)
Net loss	(2)
Employer contributions	12.0
Company's expected additional annual contribution	12.0
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	3	3	2
Change in accumulated other comprehensive income (loss)	(2)	2
Change in accumulated other comprehensive income (loss) after tax	(1)	1
Net actuarial loss arising during the year	(2)
Employer contributions	0.1
Company's expected additional annual contribution	1.0
United States Postretirement Benefit Plan of US Entity, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan included in accumulated other comprehensive income (loss)	(41)	16
Defined benefit plan included in accumulated other comprehensive income (loss) after tax	$ (24)	$ 10