Stock-based Compensation - Schedule of Nonvested Stock Awards and Performance Shares (Details) - $ / shares	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Performance-based restricted stock
Shares [Roll Forward]
Beginning of period (in shares)	668,766	448,693	252,022
Granted (in shares)	165,085	263,696	231,624
Vested (in shares)	0	0	0
Forfeited (in shares)	(189,066)	(43,623)	(34,953)
End of period (in shares)	644,785	668,766	448,693
Weighted-Average Grant Date Fair Value ($ per share) [Roll Forward]
Beginning of period (in dollars per share)	$ 15.72	$ 16.71	$ 16.34
Granted (in dollars per share)	22.40	13.60	15.43
Vested (in dollars per share)	0.00	0.00	0.00
Forfeited (in dollars per share)	18.98	13.11	5.51
End of period (in dollars per share)	$ 16.47	$ 15.72	$ 16.71
Time-based restricted stock
Shares [Roll Forward]
Beginning of period (in shares)	872,181	807,124	704,261
Granted (in shares)	277,165	271,855	259,819
Vested (in shares)	(690,922)	(189,029)	(127,993)
Forfeited (in shares)	(26,641)	(17,769)	(28,963)
End of period (in shares)	431,783	872,181	807,124
Weighted-Average Grant Date Fair Value ($ per share) [Roll Forward]
Beginning of period (in dollars per share)	$ 16.47	$ 17.52	$ 18.97
Granted (in dollars per share)	18.98	12.50	14.04
Vested (in dollars per share)	17.38	15.52	18.58
Forfeited (in dollars per share)	17.02	14.08	16.78
End of period (in dollars per share)	$ 16.60	$ 16.47	$ 17.52
Stock options
Shares [Roll Forward]
Beginning of period (in shares)	1,540,947	1,255,817	956,283
Granted (in shares)	442,250	535,551	491,443
Vested (in shares)	(690,922)	(189,029)	(127,993)
Forfeited (in shares)	(215,707)	(61,392)	(63,916)
End of period (in shares)	1,076,568	1,540,947	1,255,817
Weighted-Average Grant Date Fair Value ($ per share) [Roll Forward]
Beginning of period (in dollars per share)	$ 16.15	$ 17.23	$ 18.27
Granted (in dollars per share)	20.26	13.04	14.69
Vested (in dollars per share)	17.38	15.52	18.58
Forfeited (in dollars per share)	18.74	13.39	10.62
End of period (in dollars per share)	$ 16.53	$ 16.15	$ 17.23

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(3)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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