Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net margin	$ 57,837	$ 51,265
Adjustments to reconcile net margin to net cash provided by operating activities:
Depreciation and amortization, including nuclear fuel	278,872	281,049
Accretion cost	40,830	36,361
Amortization of deferred gains	(1,341)	(1,341)
Allowance for equity funds used during construction	(306)	(569)
Deferred outage costs	(36,502)	(26,925)
Gain on sale of investments	(14,122)	(4,611)
Regulatory deferral of costs associated with nuclear decommissioning	(11,482)	(17,686)
Other	(2,566)	(549)
Change in operating assets and liabilities:
Receivables	(22,751)	(1,706)
Inventories	3,836	(13,238)
Prepayments and other current assets	(30,914)	(2,256)
Accounts payable	(28,764)	(60,068)
Accrued interest	10,483	6,147
Accrued taxes	35,004	34,435
Other current liabilities	(16,433)	(26,761)
Member power bill prepayments	(56,975)	(94,398)
Rate management program collections	114,006	37,982
Total adjustments	260,875	145,866
Net cash provided by operating activities	318,712	197,131
Cash flows from investing activities:
Property additions	(983,902)	(887,160)
Activity in nuclear decommissioning trust fund—Purchases	(393,369)	(281,821)
Activity in nuclear decommissioning trust fund - Proceeds	387,277	275,545
Increase (decrease) in restricted investments	(7,282)	89,175
Activity in other long-term investments—Purchases	(285,842)	(165,743)
Activity in other long-term investments - Proceeds	136,476	134,907
Other	9,075	(9,674)
Net cash used in investing activities	(1,137,567)	(844,771)
Cash flows from financing activities:
Long-term debt proceeds	2,045,685	683,008
Long-term debt payments	(1,274,196)	(477,360)
(Decrease) increase in short-term borrowings, net	(16,255)	124,044
Other	(1,123)	(7,631)
Net cash provided by financing activities	754,111	322,061
Net decrease in cash and cash equivalents	(64,744)	(325,579)
Cash and cash equivalents at beginning of period	448,612	752,618
Cash and cash equivalents at end of period	383,868	427,039
Cash paid for—
Interest (net of amounts capitalized)	139,878	156,370
Supplemental disclosure of non-cash investing and financing activities:
Change in asset retirement obligations	22,086	5,053
Accrued property additions at end of period	94,365	103,390
Interest paid-in-kind	$ 0	$ 55,767