Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Statement of Stockholders' Equity [Abstract]
Cash dividends paid on common stock (in dollars per share)	$ 0.74	$ 0.56	$ 0.36