Stockholders’ Equity - RSU activity (Details) - RSUs	3 Months Ended
	Dec. 31, 2017 $ / shares shares
Number of Shares
Balance unvested at the beginning of the period (in shares) | shares	1,045,187
Granted (in shares) | shares	326,281
Vested (in shares) | shares	(123,237)
Forfeited (in shares) | shares	(212,420)
Balance unvested at the end of the period (in shares) | shares	1,035,811
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	61.14
Vested (in dollars per share) | $ / shares	46.54
Forfeited (in dollars per share) | $ / shares	47.93
Balance unvested at the end of the period (in dollars per share) | $ / shares	$ 50.17