Stock-Based Compensation Stock-Based Compensation Narrative (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
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	3.1
Unrecognized compensation expense, Expected weighted average period for recognition	2 years 6 months
Stock Options Expiration Period	10 years
Restricted Stock Units (RSUs) [Member]
[Line Items]
Award vesting rights	Restricted stock units generally vest over a three year period.
Unrecognized compensation expense	21.7
Unrecognized compensation expense, Expected weighted average period for recognition	1 year 10 months 24 days
Long Term Performance Restricted Stock Award [Member]
[Line Items]
Restricted Awards Eligible For Vesting	0	61,500	132,980
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	600,000
Stock Incentive Plan [Member]
[Line Items]
Number of shares authorized for issuance under the Stock Incentive Plan	3,500,000
Number of shares available for future grant under the Stock Incentive Plan	1,383,780