Consolidated Statements of Revenues and Expenses - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating revenues:
Total operating revenues	$ 358,860	$ 365,921	$ 715,460	$ 739,567
Operating expenses:
Fuel	111,450	122,144	210,442	242,591
Production	105,584	101,891	208,904	203,163
Depreciation and amortization	60,334	56,841	122,638	113,629
Purchased power	16,635	14,761	32,699	30,649
Accretion	13,145	9,435	23,033	18,756
Total operating expenses	307,148	305,072	597,716	608,788
Operating margin	51,712	60,849	117,744	130,779
Other income:
Investment income	14,250	14,719	30,985	28,683
Other	(886)	1,643	942	3,617
Total other income	13,364	16,362	31,927	32,300
Interest charges:
Interest expense	99,729	93,856	201,177	184,427
Allowance for debt funds used during construction	(46,910)	(36,981)	(90,337)	(72,081)
Amortization of debt discount and expense	2,874	3,051	5,852	6,049
Net interest charges	55,693	59,926	116,692	118,395
Net margin	9,383	17,285	32,979	44,684
Members
Operating revenues:
Total operating revenues	358,736	365,811	715,206	739,212
Non-Members
Operating revenues:
Total operating revenues	$ 124	$ 110	$ 254	$ 355