Employee Benefit Plans (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2012 Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan employer contribution	$ 31,100,000			$ 11,900,000
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year						51,400,000
Defined contribution plan expense		12,700,000	8,800,000	25,600,000	17,800,000
Number of shares of treasury stock used to fund in defined contribution retirement plan					461,151
Repurchased common stock issued under defined contribution plan				$ 0	$ 17,307,000