Summary of Significant Accounting Policies (Allowance For Doubtful Accounts) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of Significant Accounting Policies [Abstract]
Balance at beginning of year	$ 2,885	$ 1,191	$ 3,123
Additions [Abstract]
Charged to costs and expense	6,209	4,756	3,289
Recovery of previous write-offs	2,034	852	1,316
Uncollectible receivables written off	8,113	3,914	6,537
Balance at end of year	$ 3,015	$ 2,885	$ 1,191