Consolidated Statements of Revenues and Expenses - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating revenues:
Total operating revenues	$ 356,600	$ 373,646
Operating expenses:
Fuel	98,992	120,447
Production	103,320	101,272
Depreciation and amortization	62,303	56,788
Purchased power	16,065	15,888
Accretion	9,888	9,320
Total operating expenses	290,568	303,715
Operating margin	66,032	69,931
Other income:
Investment income	16,735	13,964
Other	1,829	1,974
Total other income	18,564	15,938
Interest charges:
Interest expense	101,448	90,571
Allowance for debt funds used during construction	(43,426)	(35,100)
Amortization of debt discount and expense	2,978	2,998
Net interest charges	61,000	58,469
Net margin	23,596	27,400
Members
Operating revenues:
Total operating revenues	356,470	373,401
Non-Members
Operating revenues:
Total operating revenues	$ 130	$ 245