Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net margin	$ 62,505	$ 42,129
Adjustments to reconcile net margin to net cash provided by operating activities:
Depreciation and amortization, including nuclear fuel	268,674	234,362
Accretion cost	24,099	19,535
Amortization of deferred gains	(1,341)	(1,341)
Allowance for equity funds used during construction	(567)	(506)
Deferred outage costs	(29,464)	(25,060)
Deferral of Hawk Road and Smith Energy Facilities effect on net margin		(41,855)
Gain on sale of investments	(653)	(34,121)
Regulatory deferral of costs associated with nuclear decommissioning	(14,522)	24,339
Other	(4,424)	(5,076)
Change in operating assets and liabilities:
Receivables	(41,015)	(4,786)
Inventories	30,251	(19,942)
Prepayments and other current assets	(1,305)	(4,650)
Accounts payable	(87,056)	(45,068)
Accrued interest	(966)	(5,774)
Accrued taxes	5,348	10,099
Other current liabilities	(20,604)	(9,006)
Member power bill prepayments	32,809	27,672
Total adjustments	159,264	118,822
Net cash provided by operating activities	221,769	160,951
Cash flows from investing activities:
Property additions	(421,384)	(335,217)
Activity in nuclear decommissioning trust fund - Purchases	(307,222)	(463,544)
Activity in nuclear decommissioning trust fund - Proceeds	302,308	460,171
Increase in restricted cash and investments	(66,821)	(23,230)
Decrease (increase) in restricted short-term investments	3,519	(5,893)
Activity in other long-term investments - Purchases	(44,457)	(48,461)
Activity in other long-term investments - Proceeds	35,278	49,075
Other	2,401	(6,239)
Net cash used in investing activities	(496,378)	(373,338)
Cash flows from financing activities:
Long-term debt proceeds	634,279	289,910
Long-term debt payments	(113,328)	(124,138)
(Decrease) increase in short-term borrowings, net	(105,225)	90,132
Other	8,553	2,628
Net cash provided by financing activities	424,279	258,532
Net increase in cash and cash equivalents	149,670	46,145
Cash and cash equivalents at beginning of period	213,038	237,391
Cash and cash equivalents at end of period	362,708	283,536
Cash paid for -
Interest (net of amounts capitalized)	185,484	186,651
Supplemental disclosure of non-cash investing and financing activities:
Change in asset retirement obligations	72,097	17,390
Change in accrued property additions	(24,451)	8,984
Interest paid-in-kind	$ 34,587	$ 26,116