Stock-based Compensation - Stock Options Outstanding (Details) - Stock Options	3 Months Ended
	Dec. 31, 2017 $ / shares shares
Shares
Outstanding at beginning of period (shares) | shares	593,753
Granted (shares) | shares	23,680
Exercised (shares) | shares	1,666
Expired (shares) | shares	(56,967)
Forfeited (shares) | shares	(2,641)
Outstanding at end of period (shares) | shares	556,159
Exercisable at end of period (shares) | shares	435,432
Vested or expected to vest in the future (shares) | shares	554,381
Weighted Average Exercise Price
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 14.76
Granted (in dollars per share) | $ / shares	20.46
Exercised (in dollars per share) | $ / shares	7.56
Expired (in dollars per share) | $ / shares	23.65
Forfeited (in dollars per share) | $ / shares	13.87
Outstanding at end of period (in dollars per share) | $ / shares	14.11
Exercisable at end of period (in dollars per share) | $ / shares	14.81
Vested or expected to vest in the future (in dollars per share) | $ / shares	$ 14.11