Quarterly report pursuant to Section 13 or 15(d)

Share-Based Payments Share-Based Payments - Employee Stock Purchase Plan (Details)

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Share-Based Payments Share-Based Payments - Employee Stock Purchase Plan (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]    
Share-based compensation $ 3,123 $ 2,955
Employee Stock Purchase Plan [Member]
   
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]    
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares) 425,848  
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date 90.00%  
Number of Large Lump Sum Contributions Related to ESPP Stock Purchases 2  
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares) 4,121 4,941
Share-based Compensation Arrangement by Share-based Payment Award, Per Share Weighted Average Price of Shares Purchased (in dollars per share) $ 29.04 $ 25.82
Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) $ 3.23 $ 7.97
Share-based compensation $ 13 $ 40