Quarterly Data (unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Quarterly Data (unaudited)
Net revenues	$ 114,300	$ 115,658	$ 123,587	$ 129,201	$ 150,254	$ 141,574	$ 158,882	$ 128,851	$ 482,746	$ 579,561	$ 542,896
Gross profit	18,774	16,163	18,605	20,084	30,425	32,389	34,535	23,491	73,626	120,840	93,780
Net income	$ 5,835	$ 4,009	$ 5,297	$ 6,436	$ 12,856	$ 13,732	$ 15,151	$ 8,443	$ 21,577	$ 50,182	$ 31,128
Net income per share:
Basic (in dollars per share)	$ 0.47	$ 0.33	$ 0.43	$ 0.52	$ 1.05	$ 1.12	$ 1.24	$ 0.69	$ 1.75	$ 4.09	$ 2.55
Diluted (in dollars per share)	$ 0.47	$ 0.32	$ 0.43	$ 0.52	$ 1.04	$ 1.11	$ 1.23	$ 0.68	$ 1.74	$ 4.07	$ 2.54