Stock-based Compensation - Schedule of Nonvested Stock Awards and Performance Shares (Details) - $ / shares	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Restricted Stock
Shares [Roll Forward]
Beginning of period (in shares)	956,283	746,567	280,416
Granted (in shares)	491,443	410,192	595,567
Vested (in shares)	(127,993)	(64,719)	(113,320)
Forfeited (in shares)	(63,916)	(135,757)	(16,096)
End of period (in shares)	1,255,817	956,283	746,567
Weighted-Average Grant Date Fair Value ($ per share) [Roll Forward]
Beginning of period (in dollars per share)	$ 18.27	$ 15.76	$ 12.32
Granted (in dollars per share)	14.69	19.01	18.68
Vested (in dollars per share)	18.58	15.96	22.55
Forfeited (in dollars per share)	10.62	7.77	15.93
End of period (in dollars per share)	$ 17.23	$ 18.27	$ 15.76
Performance Shares
Shares [Roll Forward]
Vested (in shares)	0	0	0