Retirement And Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Contribution expense		$ 3.0	$ 3.0	$ 3.0
Contributions capitalized		4.0	3.0	3.0
Change in accumulated other comprehensive income (loss) after tax		1.0	15.0	(12.0)
Current period net gain (loss)	[1]	(3.0)	(15.0)	$ 11.0
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in accumulated other comprehensive income (loss)		2.0	23.0
Change in accumulated other comprehensive income (loss) after tax		2.0	14.0
Current period net gain (loss)		(4.0)
Net loss		(2.0)
Employer contributions		12.0
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in accumulated other comprehensive income (loss)		(1.0)	2.0
Change in accumulated other comprehensive income (loss) after tax		(1.0)	1.0
Current period net gain (loss)		1.0
Employer contributions		0.2
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)		(42.0)	(41.0)
Defined benefit plan included in accumulated other comprehensive income (loss) after tax		$ (25.0)	$ (24.0)

[1] Net of $0, ($10), and $8 million in taxes for the years ended December 31, 2015, 2014 and 2013, respectively.