Summary of Significant Accounting Policies (Allowance For Doubtful Accounts) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of Significant Accounting Policies [Abstract]
Balance at beginning of year	$ 3,015	$ 2,885	$ 1,191
Additions [Abstract]
Charged to costs and expense	3,087	6,209	4,756
Recovery of previous write-offs	2,041	2,034	852
Uncollectible receivables written off	5,237	8,113	3,914
Balance at end of year	$ 2,906	$ 3,015	$ 2,885