Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net margin	$ 63,685	$ 62,505
Adjustments to reconcile net margin to net cash provided by operating activities:
Depreciation and amortization, including nuclear fuel	279,898	268,674
Accretion cost	27,333	24,099
Amortization of deferred gains	(1,341)	(1,341)
Allowance for equity funds used during construction	(567)	(567)
Deferred outage costs	(32,777)	(29,464)
Gain on sale of investments	(16,478)	(653)
Regulatory deferral of costs associated with nuclear decommissioning	631	(14,522)
Other	(6,610)	(4,424)
Change in operating assets and liabilities:
Receivables	(24,650)	(41,015)
Inventories	(3,395)	30,251
Prepayments and other current assets	1,949	(1,305)
Accounts payable	68,585	(87,056)
Accrued interest	(9,347)	(966)
Accrued taxes	7,249	5,348
Other current liabilities	(13,354)	(20,604)
Member power bill prepayments	20,935	32,809
Total adjustments	298,061	159,264
Net cash provided by operating activities	361,746	221,769
Cash flows from investing activities:
Property additions	(737,146)	(421,384)
Activity in nuclear decommissioning trust fund - Purchases	(329,248)	(307,222)
Activity in nuclear decommissioning trust fund - Proceeds	323,840	302,308
Increase in restricted investments	(44,058)	(66,821)
Decrease in restricted short-term investments	574	3,519
Activity in other long-term investments - Purchases	(45,246)	(44,457)
Activity in other long-term investments - Proceeds	27,196	35,278
Other	(12,780)	2,401
Net cash used in investing activities	(816,868)	(496,378)
Cash flows from financing activities:
Long-term debt proceeds	4,517	634,279
Long-term debt payments	(240,417)	(113,328)
Increase (decrease) in short-term borrowings, net	652,401	(105,225)
Other	14,395	8,553
Net cash provided by financing activities	430,896	424,279
Net (decrease) increase in cash and cash equivalents	(24,226)	149,670
Cash and cash equivalents at beginning of period	366,290	213,038
Cash and cash equivalents at end of period	342,064	362,708
Cash paid for -
Interest (net of amounts capitalized)	187,798	185,484
Supplemental disclosure of non-cash investing and financing activities:
Change in asset retirement obligations	2,189	72,097
Change in accrued property additions	(21,904)	(24,451)
Interest paid-in-kind	$ 42,555	$ 34,587