CONDENSED CONSOLIDATED STATEMENTS OF COMMON STOCK EQUITY (Unaudited) - USD ($) $ in Thousands		Total	Common Stock	Premium on Common Stock	Accumulated Other Comprehensive (Loss) Income	Treasury Stock and Other	Retained Earnings
Balance as of beginning of period (in shares) at Sep. 30, 2020			95,949,000
Balance as of beginning of period at Sep. 30, 2020		$ 1,643,896	$ 240,243	$ 491,982	$ (44,315)	$ 8,485	$ 947,501
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		81,045					81,045
Other comprehensive income (loss)		1,043			1,043
Common stock issued:
Incentive compensation plan (in shares)			50,000
Incentive compensation plan		5,534	$ 124	5,410
Dividend reinvestment plan (in shares)	[1]		140,000
Dividend reinvestment plan	[1]	1,091		(4,502)		5,593
Cash dividend declared		(31,966)					(31,966)
Treasury stock and other		(2,429)				(2,429)
Balance as of end of period (in shares) at Dec. 31, 2020			96,139,000
Balance as of end of period at Dec. 31, 2020		1,698,214	$ 240,367	492,890	(43,272)	11,649	996,580
Balance as of beginning of period (in shares) at Sep. 30, 2020			95,949,000
Balance as of beginning of period at Sep. 30, 2020		1,643,896	$ 240,243	491,982	(44,315)	8,485	947,501
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		119,023
Other comprehensive income (loss)		3,195
Balance as of end of period (in shares) at Jun. 30, 2021			96,361,000
Balance as of end of period at Jun. 30, 2021		1,682,066	$ 240,575	498,693	(41,120)	13,407	970,511
Balance as of beginning of period (in shares) at Dec. 31, 2020			96,139,000
Balance as of beginning of period at Dec. 31, 2020		1,698,214	$ 240,367	492,890	(43,272)	11,649	996,580
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		149,809					149,809
Other comprehensive income (loss)		1,076			1,076
Common stock issued:
Incentive compensation plan (in shares)			28,000
Incentive compensation plan		1,216	$ 72	1,144
Dividend reinvestment plan (in shares)			103,000
Dividend reinvestment plan		3,579	$ 58	3,521
Common stock offering		(388)		(388)
Cash dividend declared		(32,007)					(32,007)
Treasury stock and other (in shares)			(8,000)
Treasury stock and other		334				334
Balance as of end of period (in shares) at Mar. 31, 2021			96,262,000
Balance as of end of period at Mar. 31, 2021		1,821,833	$ 240,497	497,167	(42,196)	11,983	1,114,382
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		(111,831)					(111,831)
Other comprehensive income (loss)		1,076			1,076
Common stock issued:
Incentive compensation plan (in shares)			1,000
Incentive compensation plan		59	$ 2	57
Dividend reinvestment plan (in shares)	[1]		99,000
Dividend reinvestment plan	[1]	3,980	$ 76	3,904
Common stock offering		(2,435)		(2,435)
Cash dividend declared		(32,040)					(32,040)
Treasury stock and other (in shares)			(1,000)
Treasury stock and other		1,424				1,424
Balance as of end of period (in shares) at Jun. 30, 2021			96,361,000
Balance as of end of period at Jun. 30, 2021		$ 1,682,066	$ 240,575	498,693	(41,120)	13,407	970,511
Balance as of beginning of period (in shares) at Sep. 30, 2021		95,709,662	95,710,000
Balance as of beginning of period at Sep. 30, 2021		$ 1,630,862	$ 240,644	502,584	(34,528)	(12,448)	934,610
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		111,312					111,312
Other comprehensive income (loss)		1,030			1,030
Common stock issued:
Incentive compensation plan (in shares)			147,000
Incentive compensation plan		7,502	$ 367	7,135
Dividend reinvestment plan (in shares)			105,000
Dividend reinvestment plan		3,678	$ 263	3,415
Cash dividend declared		(34,787)					(34,787)
Treasury stock and other		(2,619)				(2,619)
Balance as of end of period (in shares) at Dec. 31, 2021			95,962,000
Balance as of end of period at Dec. 31, 2021		$ 1,716,978	$ 241,274	513,134	(33,498)	(15,067)	1,011,135
Balance as of beginning of period (in shares) at Sep. 30, 2021		95,709,662	95,710,000
Balance as of beginning of period at Sep. 30, 2021		$ 1,630,862	$ 240,644	502,584	(34,528)	(12,448)	934,610
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		220,400
Other comprehensive income (loss)		$ 3,091
Balance as of end of period (in shares) at Jun. 30, 2022		96,160,232	96,160,000
Balance as of end of period at Jun. 30, 2022		$ 1,768,683	$ 241,596	518,606	(31,437)	(10,620)	1,050,538
Balance as of beginning of period (in shares) at Dec. 31, 2021			95,962,000
Balance as of beginning of period at Dec. 31, 2021		1,716,978	$ 241,274	513,134	(33,498)	(15,067)	1,011,135
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		96,035					96,035
Other comprehensive income (loss)		1,031			1,031
Common stock issued:
Incentive compensation plan (in shares)			36,000
Incentive compensation plan		1,307	$ 91	1,216
Dividend reinvestment plan (in shares)			91,000
Dividend reinvestment plan		3,721	$ 228	3,493
Cash dividend declared		(34,827)					(34,827)
Treasury stock and other (in shares)			(7,000)
Treasury stock and other		42				42
Balance as of end of period (in shares) at Mar. 31, 2022			96,082,000
Balance as of end of period at Mar. 31, 2022		1,784,287	$ 241,593	517,843	(32,467)	(15,025)	1,072,343
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		13,053					13,053
Other comprehensive income (loss)		1,030			1,030
Common stock issued:
Incentive compensation plan (in shares)			1,000
Incentive compensation plan		56	$ 3	53
Dividend reinvestment plan (in shares)	[2]		78,000
Dividend reinvestment plan	[2]	3,536	$ 0	710		2,826
Cash dividend declared		(34,858)					(34,858)
Treasury stock and other (in shares)			(1,000)
Treasury stock and other		$ 1,579				1,579
Balance as of end of period (in shares) at Jun. 30, 2022		96,160,232	96,160,000
Balance as of end of period at Jun. 30, 2022		$ 1,768,683	$ 241,596	$ 518,606	$ (31,437)	$ (10,620)	$ 1,050,538

[1] Shares sold through the DRP issued from treasury stock at average cost, which may differ from the actual market price paid.

[2] Shares sold through the DRP issued from treasury stock at average cost, which may differ from the actual market price paid.