Parent Company Financial Information (Parent Company Only) (Schedule Of Statements Of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 77,694	$ 69,340	$ 74,513
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of equipment	6,316	5,447	4,951
Amortization/accretion of premiums/discounts	6,053	8,445	8,662
Provision for deferred income taxes	2,106	5,696	6,089
Changes in:
Other assets	1,606	(936)	5,717
Income taxes receivable/payable	382	(644)	(1,398)
Accounts payable and accrued expenses	(8,184)	(9,403)	(10,732)
CASH FLOWS FROM FINANCING ACTIVITIES:
Dividends paid	(138,172)	(146,824)	(63,768)
Repurchase of common stock	(79,633)	(91,573)	(146,781)
Stock options exercised	458	12	36
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	696,954	(27,819)	20,635
CASH AND CASH EQUIVALENTS:
Beginning of year	113,886	141,705	121,070
End of year	810,840	113,886	141,705
Capitol Federal Financial Inc [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	77,694	69,340	74,513
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in excess of distribution over earnings of subsidiary	67,826	1,440	15,716
Depreciation of equipment	2	0	0
Amortization/accretion of premiums/discounts	0	74	2,196
Other, net	0	263	1,549
Provision for deferred income taxes	3,768	3,216	5,422
Changes in:
Other assets	166	(198)	(9)
Income taxes receivable/payable	(562)	(220)	(2,160)
Accounts payable and accrued expenses	(12)	(27)	33
Net cash flows provided by operating activities	148,882	73,888	97,260
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities of AFS securities	0	60,000	300,000
Principal collected on notes receivable from ESOP	1,120	2,827	2,672
Purchases of equipment	(370)	0	0
Net cash flows provided by investing activities	750	62,827	302,672
CASH FLOWS FROM FINANCING ACTIVITIES:
Net payment from subsidiary related to restricted stock awards	243	34	6,128
Dividends paid	(138,172)	(146,824)	(63,768)
Repurchase of common stock	(79,633)	(91,573)	(146,781)
Stock options exercised	458	12	36
Net cash flows used in financing activities	(217,104)	(238,351)	(204,385)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(67,472)	(101,636)	195,547
CASH AND CASH EQUIVALENTS:
Beginning of year	207,012	308,648	113,101
End of year	$ 139,540	$ 207,012	$ 308,648