Geographic Information (Long-Lived Assets By Geographic Areas) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting Information [Line Items]
Long-Lived Assets	$ 448,810	$ 377,433	$ 338,756
United States [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	426,329	361,083	324,701
Canada [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	11,105	9,536	8,947
Other Foreign Countries [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	$ 11,376	$ 6,814	$ 5,108