Energy Purchase Contracts (Tables)

12 Months Ended

Dec. 31, 2018

Energy Purchase Contracts [Line Items]

Schedule of Utility Total Expenses

	2018		2017		2016
Utility power resources	$	357,656	$	380,523	$	402,575

Future Contractual Commitments for Power Resources and Natural Gas Resources

	2019		2020		2021		2022		2023		Thereafter		Total
Power resources	$	199,239	$	174,236	$	163,608	$	162,895	$	154,935	$	990,024	$	1,844,937
Natural gas resources	70,159		61,017		37,318		33,900		33,130		298,253		533,777
Total	$	269,398	$	235,253	$	200,926	$	196,795	$	188,065	$	1,288,277	$	2,378,714

Contractual Obligations [Member]

Energy Purchase Contracts [Line Items]

Future Contractual Commitments for Power Resources and Natural Gas Resources

	2019		2020		2021		2022		2023		Thereafter		Total
Contractual obligations	$	29,474	$	33,311	$	32,291	$	28,142	$	28,859	$	195,743	$	347,820