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Revenue: Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from contracts with customers	$ 1,930,834	$ 1,680,804	$ 1,726,392
Revenue	1,949,102	1,696,941	1,734,900
Services transferred at a point in time
Revenue from contracts with customers	27,141	27,089	27,180
Services transferred over time
Revenue from contracts with customers	1,903,693	1,653,715	1,699,212
Other revenues
Revenue	18,268	16,137	8,508
Intercompany Eliminations
Revenue from contracts with customers	(17,628)	(16,298)	(14,485)
Revenue	(18,021)	(16,586)	(14,485)
Intercompany Eliminations | Services transferred at a point in time
Revenue from contracts with customers	0	0	0
Intercompany Eliminations | Services transferred over time
Revenue from contracts with customers	(17,628)	(16,298)	(14,485)
Intercompany Eliminations | Other revenues
Revenue	(393)	(288)	0
Electric Utilities
Revenue from contracts with customers	836,923	732,681	731,231
Revenue	842,258	738,857	739,355
Electric Utilities | Services transferred at a point in time
Revenue from contracts with customers	27,141	27,089	27,180
Electric Utilities | Services transferred over time
Revenue from contracts with customers	809,782	705,592	704,051
Electric Utilities | Other revenues
Revenue	5,335	6,176	8,124
Gas Utilities
Revenue from contracts with customers	1,111,539	964,421	1,009,646
Revenue	1,124,865	974,670	1,010,030
Gas Utilities | Services transferred at a point in time
Revenue from contracts with customers	0	0	0
Gas Utilities | Services transferred over time
Revenue from contracts with customers	1,111,539	964,421	1,009,646
Gas Utilities | Other revenues
Revenue	13,326	10,249	384
Retail
Revenue from contracts with customers	1,625,173	1,402,824	1,450,776
Retail | Intercompany Eliminations
Revenue from contracts with customers	0	0	0
Retail | Electric Utilities
Revenue from contracts with customers	711,448	636,902	632,936
Retail | Gas Utilities
Revenue from contracts with customers	913,725	765,922	817,840
Transportation
Revenue from contracts with customers	157,625	154,055	142,348
Transportation | Intercompany Eliminations
Revenue from contracts with customers	(428)	(526)	(1,042)
Transportation | Electric Utilities
Revenue from contracts with customers	0	0	0
Transportation | Gas Utilities
Revenue from contracts with customers	158,053	154,581	143,390
Wholesale
Revenue from contracts with customers	30,848	24,845	28,464
Wholesale | Intercompany Eliminations
Revenue from contracts with customers	0	0	0
Wholesale | Electric Utilities
Revenue from contracts with customers	30,848	24,845	28,464
Wholesale | Gas Utilities
Revenue from contracts with customers	0	0	0
Market - off-system sales
Revenue from contracts with customers	42,078	15,772	16,772
Market - off-system sales | Intercompany Eliminations
Revenue from contracts with customers	0	0	0
Market - off-system sales | Electric Utilities
Revenue from contracts with customers	41,682	15,512	16,081
Market - off-system sales | Gas Utilities
Revenue from contracts with customers	396	260	691
Transmission/Other
Revenue from contracts with customers	75,110	83,308	88,032
Transmission/Other | Intercompany Eliminations
Revenue from contracts with customers	(17,200)	(15,772)	(13,443)
Transmission/Other | Electric Utilities
Revenue from contracts with customers	52,945	55,422	53,750
Transmission/Other | Gas Utilities
Revenue from contracts with customers	$ 39,365	$ 43,658	$ 47,725

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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