Accumulated Other Comprehensive Income (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Accumulated other comprehensive income (loss) components which were reclassified to the Condensed Consolidated Statement of Income
General and administrative	$ 34,431	$ 32,836	$ 66,674	$ 65,257
Income tax provision	100,838	81,085	190,601	167,807
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss) components which were reclassified to the Condensed Consolidated Statement of Income
Net of tax	(12,739)	432	(12,592)	865
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Unrealized gains on available-for-sale securities
Accumulated other comprehensive income (loss) components which were reclassified to the Condensed Consolidated Statement of Income
Gain on sale of investment securities	(21,352)		(21,352)
Income tax provision	8,468		8,468
Net of tax	(12,884)		(12,884)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Defined Benefit Pension Items Amortization of net actuarial loss
Accumulated other comprehensive income (loss) components which were reclassified to the Condensed Consolidated Statement of Income
General and administrative	229	685	458	1,370
Income tax provision	(84)	(253)	(166)	(505)
Net of tax	$ 145	$ 432	$ 292	$ 865