Employee Benefit Plans (Narrative) (Details) (USD $)	3 Months Ended		4 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Apr. 30, 2012	Dec. 31, 2012 Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan employer contribution			$ 11,900,000
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year				51,400,000
Defined contribution plan expense	12,900,000	9,000,000
Number of shares of treasury stock used to fund in defined contribution retirement plan		237,184
Repurchased common stock issued under defined contribution plan		$ 8,589,000