Supplemental Consolidated Quarterly Financial Data (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 50,388,000	$ 48,105,000	$ 46,571,000	$ 44,302,000	$ 41,385,000	$ 40,464,000	$ 39,532,000	$ 34,795,000	$ 189,366,000	$ 156,176,000	$ 127,855,000
Operating income (loss)	13,043,000	13,975,000	13,921,000	11,443,000	5,895,000	7,733,000	6,668,000	3,795,000	52,382,000	24,091,000	6,154,000
Income (loss) before income taxes	12,862,000	13,783,000	13,795,000	11,327,000	5,802,000	7,701,000	6,999,000	4,795,000	51,767,000	25,297,000	6,379,000
Net income	10,029,000	8,449,000	9,343,000	7,113,000	8,325,000	7,249,000	6,818,000	5,782,000	34,934,000	28,174,000	5,677,000
Diluted earnings (loss) per share	$ 0.32	$ 0.28	$ 0.31	$ 0.24	$ 0.28	$ 0.25	$ 0.24	$ 0.21	$ 1.14	$ 0.96	$ 0.20
Weighted average common shares outstanding, diluted	30,936,000	30,710,000	30,348,000	30,017,000	29,828,000	29,275,000	28,655,000	28,109,000	30,676,687	29,261,348	28,686,255
Accrued foreign tax payable	0				2,824,000				0	2,824,000
Liability for uncertain tax positions					1,600,000					1,600,000
Decrease in valuation allowance										$ 12,700,000