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 loss	(15,087)			(15,087)
Other comprehensive income (loss), net of tax	13,624				13,624
Capital contributions and issuance of common stock	506,656	$ 276	506,380
Capital contributions and issuance of common stock, Shares		27,497
Equity-based compensation	28,795		28,795
Repurchase of common stock and distributions	(2,922)	$ (2)	(2,920)
Repurchase of common stock, Shares		(110)
Reclassification of effects of tax reform enactment				3,466	(3,466)
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 loss	(8,827)			(8,827)
Other comprehensive income (loss), net of tax	(2,490)				(2,490)
Capital contributions and issuance of common stock		$ 5	(5)
Capital contributions and issuance of common stock, Shares		492
Equity-based compensation	5,908		5,908
Adoption of ASU No. 2014-09 (refer to Note 2) | Accounting Standards Update 2014-09	(1,092)			(1,092)
Balance at Dec. 31, 2018	$ 1,220,826	$ 1,050	$ 1,432,247	$ (199,555)	$ (12,916)
Balance, Shares at Dec. 31, 2018		104,962