Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income (loss)	$ (35,209)	$ 6,089	$ 81,739	$ 97,370
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization of electric plant in service	26,466	25,126	103,412	97,694
Amortization of Nuclear Fuel	10,739	10,706
Deferred income taxes, net	(10,718)	1,236
Allowance for equity funds used during construction	(586)	(1,001)
Other amortization and accretion	4,937	5,173
Net losses (gains) on decommissioning trust funds	33,164	(15,989)
Other operating activities	(163)	349
Change in:
Accounts receivable	9,021	8,352
Inventories	1,718	(2,110)
Prepayments and other	(4,403)	(5,519)
Accounts payable	(22,071)	(11,021)
Taxes accrued	(12,110)	(8,827)
Interest accrued	4,724	2,971
Net over-collection (under-collection) of fuel revenues	(6,174)	12,799
Other current liabilities	2,694	1,599
Deferred charges and credits	(3,513)	(3,513)
Net cash provided by (used for) operating activities	(1,484)	26,420
Cash flows from investing activities:
Cash additions to utility property, plant and equipment	(50,897)	(52,428)
Cash additions to nuclear fuel	(12,590)	(9,502)
Proceeds from insurance	4,591	0
Capitalized interest and AFUDC:
Utility property, plant and equipment	(1,471)	(1,973)
Nuclear fuel and other	(1,378)	(1,532)
Allowance for equity funds used during construction	586	1,001
Decommissioning trust funds:
Purchases, including funding of $0.5 million and $0.5 million, respectively	(3,073)	(37,613)
Sales and maturities	1,406	35,468
Other investing activities	829	(724)
Net cash used for investing activities	(61,997)	(67,303)
Cash flows from financing activities:
Dividends paid	(15,696)	(14,658)
Borrowings under the revolving credit facility:
Proceeds	202,095	215,196
Payments	(75,115)	(61,452)
Payment on repurchase of pollution control bonds	0	(63,500)
Other financing activities	(1,242)	(653)
Net cash provided by financing activities	110,042	74,933
Net increase in cash, cash equivalents and restricted cash	46,561	34,050
Cash, cash equivalents and restricted cash at beginning of period	10,818	12,900	46,950
Cash, cash equivalents and restricted cash at end of period	$ 57,379	$ 46,950	$ 57,379	$ 46,950