Summary Of Operations And Significant Accounting Policies (Revenues Attributable To Domestic And Foreign Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Revenue	$ 42,475	$ 39,670	$ 38,505	$ 36,759	$ 36,509	$ 34,347	$ 31,851	$ 30,382	$ 157,409	$ 133,089	$ 109,862
United States [Member]
Segment Reporting Information [Line Items]
Revenue									118,208	101,519	84,725
United Kingdom [Member]
Segment Reporting Information [Line Items]
Revenue									22,125	18,250	14,110
Other Countries [Member]
Segment Reporting Information [Line Items]
Revenue									$ 17,076	$ 13,320	$ 11,027