Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Sep. 30, 2017		$ 1,781,806	$ 677	$ 1,047,506	$ 748,186	$ (14,563)
Balance (in shares) at Sep. 30, 2017			67,700,858
Issuance of common stock, net of shares withheld for taxes		1,384	$ 3	1,381
Issuance of common stock, net of shares withheld for taxes (Shares)			342,426
Issuance costs related to secondary offering of common stock		(474)		(474)
Stock-based compensation		7,835		7,835
Other comprehensive income (loss)		(1,971)				(1,971)
Net income (loss)		941			941
Dividends on preferred shares	[1]	(6,000)			(6,000)
Balance at Mar. 31, 2018		1,783,521	$ 680	1,056,248	743,127	(16,534)
Balance (in shares) at Mar. 31, 2018			68,043,284
Balance at Dec. 31, 2017		1,852,344	$ 679	1,050,389	815,782	(14,506)
Balance (in shares) at Dec. 31, 2017			67,972,383
Issuance of common stock, net of shares withheld for taxes		1,529	$ 1	1,528
Issuance of common stock, net of shares withheld for taxes (Shares)			70,901
Issuance costs related to secondary offering of common stock		(45)		(45)
Stock-based compensation		4,376		4,376
Other comprehensive income (loss)		(2,028)				(2,028)
Net income (loss)		(66,655)			(66,655)
Dividends on preferred shares	[1]	(6,000)			(6,000)
Balance at Mar. 31, 2018		1,783,521	$ 680	1,056,248	743,127	(16,534)
Balance (in shares) at Mar. 31, 2018			68,043,284
Balance at Sep. 30, 2018		1,884,305	$ 681	1,067,040	833,834	(17,250)
Balance (in shares) at Sep. 30, 2018			68,135,790
Issuance of common stock, net of shares withheld for taxes		(2,058)	$ 3	(2,061)
Issuance of common stock, net of shares withheld for taxes (Shares)			340,081
Stock-based compensation		8,264		8,264
Other comprehensive income (loss)		(2,390)				(2,390)
Net income (loss)		(68,979)			(68,979)
Dividends on preferred shares	[1]	(12,000)			(12,000)
Balance at Mar. 31, 2019		1,807,142	$ 684	1,073,243	752,855	(19,640)
Balance (in shares) at Mar. 31, 2019			68,475,871
Balance at Dec. 31, 2018		1,874,176	$ 684	1,067,711	826,941	(21,160)
Balance (in shares) at Dec. 31, 2018			68,432,707
Issuance of common stock, net of shares withheld for taxes		725		725
Issuance of common stock, net of shares withheld for taxes (Shares)			43,164
Stock-based compensation		4,807		4,807
Other comprehensive income (loss)		1,520				1,520
Net income (loss)		(68,086)			(68,086)
Dividends on preferred shares	[1]	(6,000)			(6,000)
Balance at Mar. 31, 2019		$ 1,807,142	$ 684	$ 1,073,243	$ 752,855	$ (19,640)
Balance (in shares) at Mar. 31, 2019			68,475,871

[1] Amount represents dividends that have been declared and paid during the respective periods presented.