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, 2016	$ 722,589	$ 772	$ 892,211	$ (140,566)	$ (29,828)
Balance, Shares at Sep. 30, 2016		77,127
Net (loss) income	(37,873)			(37,873)
Other comprehensive income, net of tax	7,716				7,716
Capital contributions and issuance of common stock, Shares		(14)
Equity-based compensation	2,637		2,637
Repurchase of common stock	(558)	$ (1)	(557)
Repurchase of common stock, Shares		(58)
Balance at Jun. 30, 2017	694,511	$ 771	894,291	(178,439)	(22,112)
Balance, Shares at Jun. 30, 2017		77,055
Balance at Sep. 30, 2017	696,261	$ 771	894,089	(178,015)	(20,584)
Balance, Shares at Sep. 30, 2017		77,083
Net (loss) income	(4,139)			(4,139)
Other comprehensive income, net of tax	11,311				11,311
Capital contributions and issuance of common stock	99		99
Capital contributions and issuance of common stock, Shares		922
Equity-based compensation	20,753		20,753
Repurchase of common stock	(2,916)	$ (2)	(2,914)
Repurchase of common stock, 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