Dividends and Share Repurchases (Details) - $ / shares			3 Months Ended		6 Months Ended
	Apr. 30, 2018	Feb. 23, 2018	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Dividends Payable [Line Items]
Cash dividends per share (in dollars per share)		$ 0.17	$ 0.17	$ 0.4	$ 0.32	$ 0.54
Stock repurchased (in shares)			1,673,436
Average cost per share (in dollars per share)			$ 34.66
Warrants outstanding (in shares)			112,649		112,649
Remaining shares authorized to be repurchased (in shares)			4,080,149		4,080,149
2008 Troubled Asset Relief Program
Dividends Payable [Line Items]
Stock issued during period (in shares)			0
Subsequent Event
Dividends Payable [Line Items]
Dividends declared (in dollars per share)	$ 0.17