Stock-Based Compensation Stock-Based Compensation Narrative (Details) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011
Stock Incentive Plan [Member]
[Line Items]
Number of shares authorized for issuance under the share based compensation plan	3,500,000
Number of shares available for future grant under the Stock Incentive Plan	1,338,142
Employee Stock Option [Member]
[Line Items]
Award vesting rights	Options generally become exercisable in three equal annual installments beginning one year from the date of grant
Unrecognized compensation expense	$ 1.5
Unrecognized compensation expense, Expected weighted average period for recognition (years)	1.7
Stock options expiration period (years)	10
Restricted Stock Units (RSUs) [Member]
[Line Items]
Unrecognized compensation expense	$ 25.8
Unrecognized compensation expense, Expected weighted average period for recognition (years)	2.0
Award vesting period	Restricted stock units generally vest over a three year period.
Granted, Weighted Average Grant Date Fair Value	$ 47.29	[1]	$ 54.82	[1]
Long Term Performance Restricted Stock Award [Member]
[Line Items]
Granted, Weighted Average Grant Date Fair Value	$ 44.07
Employee Stock [Member]
[Line Items]
ESPP, percentage discount from market price on purchase date	15.00%
ESPP, maximum percentage of employee salary eligible for participation	10.00%
Shares available for future issuance under the ESPP	625,000
Maximum [Member] | Long Term Performance Restricted Stock Award [Member]
[Line Items]
Maximum number of RSUs that may become eligible for vesting related to performance awards granted in the year	208,000

[1] These restricted stock units do not include the respective 2011 and 2012 awards under the Performance Award Agreement, which are not eligible for vesting as of September 30 of each respective year.