Calculation of Weighted Average Common Shares and Common Equivalent Shares Outstanding (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net income	$ 24,176	$ 22,013
Less: Income allocable to unvested restricted stock	(152)
Income available to common shareholders	24,024	22,013
Reallocation of participating earnings	1
Diluted income attributable to common shareholders	$ 24,025	$ 22,013
Weighted average number of common share equivalents:
Common shares used in basic earnings per share	12,947,195	12,827,918
Common share equivalents outstanding related to stock options	52,918	98,896
Total weighted average common shares and common share equivalents used in diluted earnings per share	13,000,113	12,926,814
Basic earnings per common share	$ 1.86	$ 1.72
Diluted earnings per common share	$ 1.85	$ 1.70