Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net margin	$ 44,684	$ 37,130
Adjustments to reconcile net margin to net cash provided by operating activities:
Depreciation and amortization, including nuclear fuel	184,323	185,640
Accretion cost	18,756	18,109
Amortization of deferred gains	(894)	(894)
Allowance for equity funds used during construction	(450)	(387)
Deferred outage costs	(12,411)	(22,194)
Loss (gain) on sale of investments	3,152	(16,352)
Regulatory deferral of costs associated with nuclear decommissioning	(13,966)	5,707
Other	(2,637)	(4,934)
Change in operating assets and liabilities:
Receivables	(7,254)	4,556
Inventories	2,460	(6,897)
Prepayments and other current assets	(518)	361
Accounts payable	(25,517)	27,736
Accrued interest	6,161	(31,944)
Accrued taxes	1,269	(2,641)
Other current liabilities	(7,600)	(4,852)
Member power bill prepayments	12,239	(48,831)
Other	6,188
Total adjustments	163,301	102,183
Net cash provided by operating activities	207,985	139,313
Cash flows from investing activities:
Property additions	(561,033)	(474,683)
Activity in nuclear decommissioning trust fund - Purchases	(262,959)	(235,754)
Activity in nuclear decommissioning trust fund - Proceeds	259,092	232,376
Decrease in restricted investments	68,474	12,147
Decrease in restricted short-term investments	9,335	61,889
Activity in other long-term investments - Purchases	(102,715)	(39,042)
Activity in other long-term investments - Proceeds	90,329	25,390
Other	10,473	(2,225)
Net cash used in investing activities	(489,004)	(419,902)
Cash flows from financing activities:
Long-term debt proceeds	236,200	4,517
Long-term debt payments	(77,234)	(240,182)
Increase in short-term borrowings, net	247,395	425,929
Other	1,837	10,141
Net cash provided by financing activities	408,198	200,405
Net increase (decrease) in cash and cash equivalents	127,179	(80,184)
Cash and cash equivalents at beginning of period	397,695	366,290
Cash and cash equivalents at end of period	524,874	286,106
Cash paid for -
Interest (net of amounts capitalized)	104,670	150,849
Supplemental disclosure of non-cash investing and financing activities:
Change in asset retirement obligations	2,404	0
Accrued property additions at end of period	141,338	104,799
Interest paid-in-kind	$ 29,072	$ 28,092