Geographic Data (Schedule) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Segment Reporting Information [Line Items]
United States													$ 372,993	$ 299,994	$ 254,751
Total revenues	117,881	113,167	108,394	100,384	95,155	89,469	84,629	80,235	77,489	74,978	72,816	67,653	439,826	349,488	292,936
Europe Member
Segment Reporting Information [Line Items]
Foreign													49,963	36,260	25,963
Other
Segment Reporting Information [Line Items]
Foreign													$ 16,870	$ 13,234	$ 12,222