Stockholders’ Equity - RSU activity (Details) - RSUs	6 Months Ended
	Mar. 31, 2018 $ / shares shares
Number of Shares
Balance unvested at the beginning of the period (in shares) | shares	1,045,187
Granted (in shares) | shares	332,686
Vested (in shares) | shares	(125,837)
Forfeited (in shares) | shares	(230,391)
Balance unvested at the end of the period (in shares) | shares	1,021,645
Weighted Average Grant-Date Fair Value
Balance unvested at the beginning of the period (in dollars per share) | $ / shares	$ 45.86
Granted (in dollars per share) | $ / shares	61.13
Vested (in dollars per share) | $ / shares	46.37
Forfeited (in dollars per share) | $ / shares	48.14
Balance unvested at the end of the period (in dollars per share) | $ / shares	$ 50.26