Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net margin	$ 43,875	$ 26,221
Adjustments to reconcile net margin to net cash provided by operating activities:
Depreciation and amortization, including nuclear fuel	177,367	156,416
Accretion cost	16,040	12,859
Amortization of deferred gains	(894)	(894)
Allowance for equity funds used during construction	(352)	(342)
Deferred outage costs	(26,090)	(18,274)
Deferral of Hawk Road and Smith Energy Facilities effect on net margin		(41,689)
Loss (gain) on sale of investments	633	(32,470)
Regulatory deferral of costs associated with nuclear decommissioning	(10,677)	25,781
Other	(3,429)	(3,312)
Change in operating assets and liabilities:
Receivables	(37,697)	(11,171)
Inventories	4,386	2,857
Prepayments and other current assets	(698)	(10,664)
Accounts payable	(73,698)	(45,059)
Accrued interest	2,006	(49)
Accrued taxes	(3,597)	820
Other current liabilities	(23,977)	(8,681)
Member power bill prepayments	(24,876)	(11,033)
Total adjustments	(5,553)	15,095
Net cash provided by operating activities	38,322	41,316
Cash flows from investing activities:
Property additions	(301,545)	(239,510)
Activity in nuclear decommissioning trust fund - Purchases	(216,217)	(281,938)
Activity in nuclear decommissioning trust fund - Proceeds	212,949	279,751
Decrease in restricted cash and investments	31,574	41,855
Decrease (increase) in restricted short-term investments	1,340	(5,524)
Activity in other long-term investments - Purchases	(31,114)	(23,746)
Activity in other long-term investments - Proceeds	24,820	24,973
Other	2,494	(8,450)
Net cash used in investing activities	(275,699)	(212,589)
Cash flows from financing activities:
Long-term debt proceeds	628,358	271,892
Long-term debt payments	(75,537)	(76,418)
(Decrease) increase in short-term borrowings, net	(185,483)	27,375
Other	4,370	(2,190)
Net cash provided by financing activities	371,708	220,659
Net increase in cash and cash equivalents	134,331	49,386
Cash and cash equivalents at beginning of period	213,038	237,391
Cash and cash equivalents at end of period	347,369	286,777
Cash paid for -
Interest (net of amounts capitalized)	121,760	127,026
Supplemental disclosure of non-cash investing and financing activities:
Change in asset retirement obligations	70,780	20,711
Change in accrued property additions	(38,209)	(8,454)
Interest paid-in-kind	$ 21,765	$ 16,528