Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Balance at Sep. 30, 2017	$ 696,261	$ 771	$ 894,089	$ (178,015)	$ (20,584)
Balance, Shares at Sep. 30, 2017		77,083
Net income (loss)	(4,139)			(4,139)
Other comprehensive income (loss), net of tax	11,311				11,311
Capital contributions and issuance of common stock, net of forfeitures	99		99
Capital contributions and issuance of common stock, net of forfeitures, Shares		922
Equity-based compensation	20,753		20,753
Repurchase of common stock and distributions	(2,916)	$ (2)	(2,914)
Repurchase of common stock and distributions, Shares		(110)
Reclassification of effects of tax reform enactment				3,466	(3,466)
Balance at Jun. 30, 2018	721,369	$ 769	912,027	(178,688)	(12,739)
Balance, Shares at Jun. 30, 2018		77,895
Balance at Mar. 31, 2018	704,614	$ 770	897,187	(177,289)	(16,054)
Balance, Shares at Mar. 31, 2018		76,985
Net income (loss)	(1,397)			(1,397)
Other comprehensive income (loss), net of tax	3,315				3,315
Capital contributions and issuance of common stock, net of forfeitures, Shares		910
Equity-based compensation	14,951		14,951
Repurchase of common stock and distributions	(112)	$ (1)	(111)
Other	(2)			(2)
Balance at Jun. 30, 2018	721,369	$ 769	912,027	(178,688)	(12,739)
Balance, Shares at Jun. 30, 2018		77,895
Balance at Sep. 30, 2018	1,227,327	$ 1,045	1,426,344	(189,636)	(10,426)
Balance, Shares at Sep. 30, 2018		104,470
Net income (loss)	19,276			19,276
Other comprehensive income (loss), net of tax	(2,509)				(2,509)
Capital contributions and issuance of common stock, net of forfeitures	1	$ 4	(3)
Capital contributions and issuance of common stock, net of forfeitures, Shares		372
Equity-based compensation	11,826		11,826
Adoption of ASU No. 2014-09 (Refer to Note 2) | Accounting Standards Update 2014-09	(1,092)			(1,092)
Balance at Jun. 30, 2019	1,254,829	$ 1,049	1,438,167	(171,452)	(12,935)
Balance, Shares at Jun. 30, 2019		104,842
Balance at Mar. 31, 2019	1,223,964	$ 1,050	1,437,859	(203,161)	(11,784)
Balance, Shares at Mar. 31, 2019		104,962
Net income (loss)	31,709			31,709
Other comprehensive income (loss), net of tax	(1,151)				(1,151)
Capital contributions and issuance of common stock, net of forfeitures		$ (1)	1
Capital contributions and issuance of common stock, net of forfeitures, Shares		(120)
Equity-based compensation	307		307
Balance at Jun. 30, 2019	$ 1,254,829	$ 1,049	$ 1,438,167	$ (171,452)	$ (12,935)
Balance, Shares at Jun. 30, 2019		104,842