Income Taxes Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax at statutory rate of 35%	$ 211,433	$ 189,764	$ 173,310
Common stock dividends deductible for tax reporting	(2,584)	(2,570)	(2,413)
State taxes (net of federal benefit)	16,100	11,133	12,289
Change in valuation allowance	0	1,324	4,998
Other, net	(3,566)	(3,009)	1,365
Income tax expense (benefit)	$ 221,383	$ 196,642	$ 189,549