Employee Benefit Plans (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Estimated average life of plan, years	15
Target allocation, equity securities, minimum (percent)	55.00%
Target allocation, equity securities, maximum (percent)	65.00%
Target allocation, fixed income, minimum	35.00%
Target allocation, fixed income, maximum (percent)	45.00%
Core matching cash contributions of employee contributions	100.00%
Qualified earnings contributed by employees potentially eligible for matching	4.00%
Defined contribution match expense	$ 20,000,000	$ 19,000,000	$ 20,000,000
Annual contribution to the individual account of each eligible employee, minimum percent of annual compensation	3.00%
Annual contribution to the individual account of each eligible employee, maximum percent of annual compensation	8.00%
Defined contribution feature expense	4,000,000	3,000,000	3,000,000
Pension Plans, Defined Benefit [Member]
Defined benefit pension expense	47,000,000	30,000,000	57,000,000
Non Qualified Plans [Member] | Pension Plans, Defined Benefit [Member]
Defined benefit pension expense	19,000,000	14,000,000	20,000,000
Defined benefit pension plan, fair value	$ 0	$ 0