Retirement Benefits (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Number of high-quality corporate bonds		500
Defined benefit plan, high-quality bond maturity, minimum range used to determine yield curve, in years		0
Defined benefit plan, high-quality bond maturity, maximum range used to determine yield curve, in years		30
Defined benefit plan, estimated future employer contributions during the next five years		580
Actual return in excess of (or less than) expected return, percentage		25.00%
Amortization basis, straight line, in years		10
Number Of Employees Who Moved To A Cash Balance Formula [Member]
Number of employees		430	700
Pension Benefits [Member]
Expected return on plan assets	7.75%	8.00%	8.00%	8.00%
Postretirement Benefits [Member]
Expected return on plan assets	7.50%	7.75%	8.00%	8.00%
Minimum [Member]
Defined benefit plan, estimated future employer contributions during the next five years		90
Maximum [Member]
Defined benefit plan, estimated future employer contributions during the next five years		150
Private Equity [Member]
Number of limited partnerships in private equity funds		10
Minimum invested capital within limited partnership investments		0.1
Maximum invested capital within limited partnership investments		7