Retirement And Employee Benefit Plans (Changes In The Plans Benefit Obligations, Fair Value Of Assets, And Funded Status) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 13	$ 14	$ 11
Interest cost	5	4	4
Employer contributions	12.0
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	2
Interest cost	1	1
Employer contributions	0.1
Change In Benefit Obligation [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at January 1	103	105
Service cost	13	14
Interest cost	5	4
Actuarial loss	21	(11)
Benefits paid	(8)	(8)
Settlements		(1)
Benefit obligation at December 31	134	103
Change In Benefit Obligation [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at January 1	12	12
Service cost	2	2
Interest cost	1
Actuarial loss	3	(2)
Benefit obligation at December 31	18	12
Change In Plan Assets [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	12.0	13.0
Benefits paid	(8)	(8)
Settlements		(1)
Fair value of plan assets at January 1	99	83
Fair value of plan assets at December 31	108	99
Actual return/(loss) on plan assets	5	12
Funded status of plans at December 31	(26)	(4)
Change In Plan Assets [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Funded status of plans at December 31	$ (18)	$ (12)